Revert 189830 "cc: Chromify LayerTreeHostCommon"

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/layer_iterator.h"
 #include "cc/layers/render_surface.h"
 #include "cc/layers/render_surface_impl.h"
 #include "cc/trees/layer_sorter.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
-ScrollAndScaleSet::ScrollAndScaleSet() {}
-
-ScrollAndScaleSet::~ScrollAndScaleSet() {}
-
-static void SortLayers(std::vector<scoped_refptr<Layer> >::iterator forst,
-                       std::vector<scoped_refptr<Layer> >::iterator end,
-                       void* layer_sorter) {
-  NOTREACHED();
-}
-
-static void SortLayers(std::vector<LayerImpl*>::iterator first,
-                       std::vector<LayerImpl*>::iterator end,
-                       LayerSorter* layer_sorter) {
-  DCHECK(layer_sorter);
-  TRACE_EVENT0("cc", "LayerTreeHostCommon::SortLayers");
-  layer_sorter->Sort(first, end);
-}
-
-inline gfx::Rect CalculateVisibleRectWithCachedLayerRect(
-    gfx::Rect target_surface_rect,
-    gfx::Rect layer_bound_rect,
-    gfx::Rect layer_rect_in_target_space,
-    const gfx::Transform& transform) {
-  // Is this layer fully contained within the target surface?
-  if (target_surface_rect.Contains(layer_rect_in_target_space))
-    return layer_bound_rect;
-
-  // If the layer doesn't fill up the entire surface, then find the part of
-  // the surface rect where the layer could be visible. This avoids trying to
-  // project surface rect points that are behind the projection point.
-  gfx::Rect minimal_surface_rect = target_surface_rect;
-  minimal_surface_rect.Intersect(layer_rect_in_target_space);
-
-  // Project the corners of the target surface rect into the layer space.
-  // This bounding rectangle may be larger than it needs to be (being
-  // axis-aligned), but is a reasonable filter on the space to consider.
-  // Non-invertible transforms will create an empty rect here.
-
-  gfx::Transform surface_to_layer(gfx::Transform::kSkipInitialization);
-  if (!transform.GetInverse(&surface_to_layer)) {
-    // TODO(shawnsingh): Either we need to handle uninvertible transforms
-    // here, or DCHECK that the transform is invertible.
-  }
-  gfx::Rect layer_rect = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
-      surface_to_layer, gfx::RectF(minimal_surface_rect)));
-  layer_rect.Intersect(layer_bound_rect);
-  return layer_rect;
-}
-
-gfx::Rect LayerTreeHostCommon::CalculateVisibleRect(
-    gfx::Rect target_surface_rect,
-    gfx::Rect layer_bound_rect,
-    const gfx::Transform& transform) {
-  gfx::Rect layer_in_surface_space =
-      MathUtil::MapClippedRect(transform, layer_bound_rect);
-  return CalculateVisibleRectWithCachedLayerRect(
-      target_surface_rect, layer_bound_rect, layer_in_surface_space, transform);
-}
-
-template <typename LayerType> static inline bool IsRootLayer(LayerType* layer) {
-  return !layer->parent();
+ScrollAndScaleSet::ScrollAndScaleSet()
+{
+}
+
+ScrollAndScaleSet::~ScrollAndScaleSet()
+{
+}
+
+static void sortLayers(std::vector<scoped_refptr<Layer> >::iterator forst, std::vector<scoped_refptr<Layer> >::iterator end, void* layerSorter)
+{
+    NOTREACHED();
+}
+
+static void sortLayers(std::vector<LayerImpl*>::iterator first, std::vector<LayerImpl*>::iterator end, LayerSorter* layerSorter)
+{
+    DCHECK(layerSorter);
+    TRACE_EVENT0("cc", "layer_tree_host_common::sortLayers");
+    layerSorter->Sort(first, end);
+}
+
+inline gfx::Rect calculateVisibleRectWithCachedLayerRect(const gfx::Rect& targetSurfaceRect, const gfx::Rect& layerBoundRect, const gfx::Rect& layerRectInTargetSpace, const gfx::Transform& transform)
+{
+    // Is this layer fully contained within the target surface?
+    if (targetSurfaceRect.Contains(layerRectInTargetSpace))
+        return layerBoundRect;
+
+    // If the layer doesn't fill up the entire surface, then find the part of
+    // the surface rect where the layer could be visible. This avoids trying to
+    // project surface rect points that are behind the projection point.
+    gfx::Rect minimalSurfaceRect = targetSurfaceRect;
+    minimalSurfaceRect.Intersect(layerRectInTargetSpace);
+
+    // Project the corners of the target surface rect into the layer space.
+    // This bounding rectangle may be larger than it needs to be (being
+    // axis-aligned), but is a reasonable filter on the space to consider.
+    // Non-invertible transforms will create an empty rect here.
+
+    gfx::Transform surfaceToLayer(gfx::Transform::kSkipInitialization);
+    if (!transform.GetInverse(&surfaceToLayer)) {
+        // TODO(shawnsingh): Either we need to handle uninvertible transforms
+        // here, or DCHECK that the transform is invertible.
+    }
+    gfx::Rect layerRect = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(surfaceToLayer, gfx::RectF(minimalSurfaceRect)));
+    layerRect.Intersect(layerBoundRect);
+    return layerRect;
+}
+
+gfx::Rect LayerTreeHostCommon::calculateVisibleRect(const gfx::Rect& targetSurfaceRect, const gfx::Rect& layerBoundRect, const gfx::Transform& transform)
+{
+    gfx::Rect layerInSurfaceSpace = MathUtil::MapClippedRect(transform, layerBoundRect);
+    return calculateVisibleRectWithCachedLayerRect(targetSurfaceRect, layerBoundRect, layerInSurfaceSpace, transform);
 }
 
 template <typename LayerType>
-static inline bool LayerIsInExisting3DRenderingContext(LayerType* layer) {
-  // According to current W3C spec on CSS transforms, a layer is part of an
-  // established 3d rendering context if its parent has transform-style of
-  // preserves-3d.
-  return layer->parent() && layer->parent()->preserves_3d();
-}
-
-template <typename LayerType>
-static bool IsRootLayerOfNewRenderingContext(LayerType* layer) {
-  // According to current W3C spec on CSS transforms (Section 6.1), a layer is
-  // the beginning of 3d rendering context if its parent does not have
-  // transform-style: preserve-3d, but this layer itself does.
-  if (layer->parent())
-    return !layer->parent()->preserves_3d() && layer->preserves_3d();
-
-  return layer->preserves_3d();
-}
-
-template <typename LayerType>
-static bool IsLayerBackFaceVisible(LayerType* layer) {
-  // The current W3C spec on CSS transforms says that backface visibility should
-  // be determined differently depending on whether the layer is in a "3d
-  // rendering context" or not. For Chromium code, we can determine whether we
-  // are in a 3d rendering context by checking if the parent preserves 3d.
-
-  if (LayerIsInExisting3DRenderingContext(layer))
-    return layer->draw_transform().IsBackFaceVisible();
-
-  // In this case, either the layer establishes a new 3d rendering context, or
-  // is not in a 3d rendering context at all.
-  return layer->transform().IsBackFaceVisible();
-}
-
-template <typename LayerType>
-static bool IsSurfaceBackFaceVisible(LayerType* layer,
-                                     const gfx::Transform& draw_transform) {
-  if (LayerIsInExisting3DRenderingContext(layer))
-    return draw_transform.IsBackFaceVisible();
-
-  if (IsRootLayerOfNewRenderingContext(layer))
+static inline bool isRootLayer(LayerType* layer)
+{
+    return !layer->parent();
+}
+
+template<typename LayerType>
+static inline bool layerIsInExisting3DRenderingContext(LayerType* layer)
+{
+    // According to current W3C spec on CSS transforms, a layer is part of an established
+    // 3d rendering context if its parent has transform-style of preserves-3d.
+    return layer->parent() && layer->parent()->preserves_3d();
+}
+
+template<typename LayerType>
+static bool isRootLayerOfNewRenderingContext(LayerType* layer)
+{
+    // According to current W3C spec on CSS transforms (Section 6.1), a layer is the
+    // beginning of 3d rendering context if its parent does not have transform-style:
+    // preserve-3d, but this layer itself does.
+    if (layer->parent())
+        return !layer->parent()->preserves_3d() && layer->preserves_3d();
+
+    return layer->preserves_3d();
+}
+
+template<typename LayerType>
+static bool isLayerBackFaceVisible(LayerType* layer)
+{
+    // The current W3C spec on CSS transforms says that backface visibility should be
+    // determined differently depending on whether the layer is in a "3d rendering
+    // context" or not. For Chromium code, we can determine whether we are in a 3d
+    // rendering context by checking if the parent preserves 3d.
+
+    if (layerIsInExisting3DRenderingContext(layer))
+        return layer->draw_transform().IsBackFaceVisible();
+
+    // In this case, either the layer establishes a new 3d rendering context, or is not in
+    // a 3d rendering context at all.
     return layer->transform().IsBackFaceVisible();
-
-  // If the render_surface is not part of a new or existing rendering context,
-  // then the layers that contribute to this surface will decide back-face
-  // visibility for themselves.
-  return false;
-}
-
-template <typename LayerType>
-static inline bool LayerClipsSubtree(LayerType* layer) {
-  return layer->masks_to_bounds() || layer->mask_layer();
-}
-
-template <typename LayerType>
-static gfx::Rect CalculateVisibleContentRect(
-    LayerType* layer,
-    gfx::Rect ancestor_clip_rect_in_descendant_surface_space,
-    gfx::Rect layer_rect_in_target_space) {
-  DCHECK(layer->render_target());
-
-  // Nothing is visible if the layer bounds are empty.
-  if (!layer->DrawsContent() || layer->content_bounds().IsEmpty() ||
-      layer->drawable_content_rect().IsEmpty())
-    return gfx::Rect();
-
-  // Compute visible bounds in target surface space.
-  gfx::Rect visible_rect_in_target_surface_space =
-      layer->drawable_content_rect();
-
-  if (!layer->render_target()->render_surface()->clip_rect().IsEmpty()) {
-    // In this case the target surface does clip layers that contribute to
-    // it. So, we have to convert the current surface's clipRect from its
-    // ancestor surface space to the current (descendant) surface
-    // space. This conversion is done outside this function so that it can
-    // be cached instead of computing it redundantly for every layer.
-    visible_rect_in_target_surface_space.Intersect(
-        ancestor_clip_rect_in_descendant_surface_space);
-  }
-
-  if (visible_rect_in_target_surface_space.IsEmpty())
-    return gfx::Rect();
-
-  return CalculateVisibleRectWithCachedLayerRect(
-      visible_rect_in_target_surface_space,
-      gfx::Rect(gfx::Point(), layer->content_bounds()),
-      layer_rect_in_target_space,
-      layer->draw_transform());
-}
-
-static inline bool TransformToParentIsKnown(LayerImpl* layer) { return true; }
-
-static inline bool TransformToParentIsKnown(Layer* layer) {
-
-  return !layer->TransformIsAnimating();
-}
-
-static inline bool TransformToScreenIsKnown(LayerImpl* layer) { return true; }
-
-static inline bool TransformToScreenIsKnown(Layer* layer) {
-  return !layer->screen_space_transform_is_animating();
-}
-
-template <typename LayerType>
-static bool LayerShouldBeSkipped(LayerType* layer) {
-  // Layers can be skipped if any of these conditions are met.
-  //   - does not draw content.
-  //   - is transparent
-  //   - has empty bounds
-  //   - the layer is not double-sided, but its back face is visible.
-  //
-  // Some additional conditions need to be computed at a later point after the
-  // recursion is finished.
-  //   - the intersection of render surface content and layer clipRect is empty
-  //   - the visibleContentRect is empty
-  //
-  // Note, if the layer should not have been drawn due to being fully
-  // transparent, we would have skipped the entire subtree and never made it
-  // into this function, so it is safe to omit this check here.
-
-  if (!layer->DrawsContent() || layer->bounds().IsEmpty())
+}
+
+template<typename LayerType>
+static bool isSurfaceBackFaceVisible(LayerType* layer, const gfx::Transform& drawTransform)
+{
+    if (layerIsInExisting3DRenderingContext(layer))
+        return drawTransform.IsBackFaceVisible();
+
+    if (isRootLayerOfNewRenderingContext(layer))
+        return layer->transform().IsBackFaceVisible();
+
+    // If the renderSurface is not part of a new or existing rendering context, then the
+    // layers that contribute to this surface will decide back-face visibility for themselves.
+    return false;
+}
+
+template<typename LayerType>
+static inline bool layerClipsSubtree(LayerType* layer)
+{
+    return layer->masks_to_bounds() || layer->mask_layer();
+}
+
+template<typename LayerType>
+static gfx::Rect calculateVisibleContentRect(LayerType* layer, const gfx::Rect& ancestorClipRectInDescendantSurfaceSpace, const gfx::Rect& layerRectInTargetSpace)
+{
+    DCHECK(layer->render_target());
+
+    // Nothing is visible if the layer bounds are empty.
+    if (!layer->DrawsContent() || layer->content_bounds().IsEmpty() || layer->drawable_content_rect().IsEmpty())
+        return gfx::Rect();
+
+    // Compute visible bounds in target surface space.
+    gfx::Rect visibleRectInTargetSurfaceSpace = layer->drawable_content_rect();
+
+    if (!layer->render_target()->render_surface()->clip_rect().IsEmpty()) {
+        // In this case the target surface does clip layers that contribute to
+        // it. So, we have to convert the current surface's clipRect from its
+        // ancestor surface space to the current (descendant) surface
+        // space. This conversion is done outside this function so that it can
+        // be cached instead of computing it redundantly for every layer.
+        visibleRectInTargetSurfaceSpace.Intersect(ancestorClipRectInDescendantSurfaceSpace);
+    }
+
+    if (visibleRectInTargetSurfaceSpace.IsEmpty())
+        return gfx::Rect();
+
+    return calculateVisibleRectWithCachedLayerRect(visibleRectInTargetSurfaceSpace, gfx::Rect(gfx::Point(), layer->content_bounds()), layerRectInTargetSpace, layer->draw_transform());
+}
+
+static inline bool transformToParentIsKnown(LayerImpl*)
+{
     return true;
-
-  LayerType* backface_test_layer = layer;
-  if (layer->use_parent_backface_visibility()) {
-    DCHECK(layer->parent());
-    DCHECK(!layer->parent()->use_parent_backface_visibility());
-    backface_test_layer = layer->parent();
-  }
-
-  // The layer should not be drawn if (1) it is not double-sided and (2) the
-  // back of the layer is known to be facing the screen.
-  if (!backface_test_layer->double_sided() &&
-      TransformToScreenIsKnown(backface_test_layer) &&
-      IsLayerBackFaceVisible(backface_test_layer))
+}
+
+static inline bool transformToParentIsKnown(Layer* layer)
+{
+
+    return !layer->TransformIsAnimating();
+}
+
+static inline bool transformToScreenIsKnown(LayerImpl*)
+{
     return true;
-
-  return false;
-}
-
-static inline bool SubtreeShouldBeSkipped(LayerImpl* layer) {
-  // The opacity of a layer always applies to its children (either implicitly
-  // via a render surface or explicitly if the parent preserves 3D), so the
-  // entire subtree can be skipped if this layer is fully transparent.
-  return !layer->opacity();
-}
-
-static inline bool SubtreeShouldBeSkipped(Layer* layer) {
-  // If the opacity is being animated then the opacity on the main thread is
-  // unreliable (since the impl thread may be using a different opacity), so it
-  // should not be trusted.
-  // In particular, it should not cause the subtree to be skipped.
-  // Similarly, for layers that might animate opacity using an impl-only
-  // animation, their subtree should also not be skipped.
-  return !layer->opacity() && !layer->OpacityIsAnimating() &&
-         !layer->OpacityCanAnimateOnImplThread();
+}
+
+static inline bool transformToScreenIsKnown(Layer* layer)
+{
+    return !layer->screen_space_transform_is_animating();
+}
+
+template<typename LayerType>
+static bool layerShouldBeSkipped(LayerType* layer)
+{
+    // Layers can be skipped if any of these conditions are met.
+    //   - does not draw content.
+    //   - is transparent
+    //   - has empty bounds
+    //   - the layer is not double-sided, but its back face is visible.
+    //
+    // Some additional conditions need to be computed at a later point after the recursion is finished.
+    //   - the intersection of render surface content and layer clipRect is empty
+    //   - the visibleContentRect is empty
+    //
+    // Note, if the layer should not have been drawn due to being fully transparent,
+    // we would have skipped the entire subtree and never made it into this function,
+    // so it is safe to omit this check here.
+
+    if (!layer->DrawsContent() || layer->bounds().IsEmpty())
+        return true;
+
+    LayerType* backfaceTestLayer = layer;
+    if (layer->use_parent_backface_visibility()) {
+        DCHECK(layer->parent());
+        DCHECK(!layer->parent()->use_parent_backface_visibility());
+        backfaceTestLayer = layer->parent();
+    }
+
+    // The layer should not be drawn if (1) it is not double-sided and (2) the back of the layer is known to be facing the screen.
+    if (!backfaceTestLayer->double_sided() && transformToScreenIsKnown(backfaceTestLayer) && isLayerBackFaceVisible(backfaceTestLayer))
+        return true;
+
+    return false;
+}
+
+static inline bool subtreeShouldBeSkipped(LayerImpl* layer)
+{
+    // The opacity of a layer always applies to its children (either implicitly
+    // via a render surface or explicitly if the parent preserves 3D), so the
+    // entire subtree can be skipped if this layer is fully transparent.
+    return !layer->opacity();
+}
+
+static inline bool subtreeShouldBeSkipped(Layer* layer)
+{
+    // If the opacity is being animated then the opacity on the main thread is unreliable
+    // (since the impl thread may be using a different opacity), so it should not be trusted.
+    // In particular, it should not cause the subtree to be skipped.
+    // Similarly, for layers that might animate opacity using an impl-only
+    // animation, their subtree should also not be skipped.
+    return !layer->opacity() && !layer->OpacityIsAnimating() &&
+           !layer->OpacityCanAnimateOnImplThread();
 }
 
 // Called on each layer that could be drawn after all information from
 // calcDrawProperties has been updated on that layer.  May have some false
 // positives (e.g. layers get this called on them but don't actually get drawn).
-static inline void UpdateTilePrioritiesForLayer(LayerImpl* layer) {
-  layer->UpdateTilePriorities();
-
-  // Mask layers don't get this call, so explicitly update them so they can
-  // kick off tile rasterization.
-  if (layer->mask_layer())
-    layer->mask_layer()->UpdateTilePriorities();
-  if (layer->replica_layer() && layer->replica_layer()->mask_layer())
-    layer->replica_layer()->mask_layer()->UpdateTilePriorities();
-}
-
-static inline void UpdateTilePrioritiesForLayer(Layer* layer) {}
-
-template <typename LayerType>
-static bool SubtreeShouldRenderToSeparateSurface(
-    LayerType* layer,
-    bool axis_aligned_with_respect_to_parent) {
-  //
-  // A layer and its descendants should render onto a new RenderSurfaceImpl if
-  // any of these rules hold:
-  //
-
-  // The root layer should always have a render_surface.
-  if (IsRootLayer(layer))
-    return true;
-
-  // If we force it.
-  if (layer->force_render_surface())
-    return true;
-
-  // If the layer uses a mask.
-  if (layer->mask_layer())
-    return true;
-
-  // If the layer has a reflection.
-  if (layer->replica_layer())
-    return true;
-
-  // If the layer uses a CSS filter.
-  if (!layer->filters().isEmpty() || !layer->background_filters().isEmpty() ||
-      layer->filter())
-    return true;
-
-  int num_descendants_that_draw_content =
-      layer->draw_properties().num_descendants_that_draw_content;
-
-  // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but
-  // it is treated as a 3D object by its parent (i.e. parent does preserve-3d).
-  if (LayerIsInExisting3DRenderingContext(layer) && !layer->preserves_3d() &&
-      num_descendants_that_draw_content > 0) {
-    TRACE_EVENT_INSTANT0(
-        "cc",
-        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface flattening");
-    return true;
-  }
-
-  // If the layer clips its descendants but it is not axis-aligned with respect
-  // to its parent.
-  bool layer_clips_external_content =
-      LayerClipsSubtree(layer) || layer->HasDelegatedContent();
-  if (layer_clips_external_content && !axis_aligned_with_respect_to_parent &&
-      !layer->draw_properties().descendants_can_clip_selves) {
-    TRACE_EVENT_INSTANT0(
-        "cc",
-        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface clipping");
-    return true;
-  }
-
-  // If the layer has some translucency and does not have a preserves-3d
-  // transform style.  This condition only needs a render surface if two or more
-  // layers in the subtree overlap. But checking layer overlaps is unnecessarily
-  // costly so instead we conservatively create a surface whenever at least two
-  // layers draw content for this subtree.
-  bool at_least_two_layers_in_subtree_draw_content =
-      num_descendants_that_draw_content > 0 &&
-      (layer->DrawsContent() || num_descendants_that_draw_content > 1);
-
-  if (layer->opacity() != 1.f && !layer->preserves_3d() &&
-      at_least_two_layers_in_subtree_draw_content) {
-    TRACE_EVENT_INSTANT0(
-        "cc",
-        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface opacity");
-    return true;
-  }
-
-  return false;
-}
-
-gfx::Transform ComputeScrollCompensationForThisLayer(
-    LayerImpl* scrolling_layer,
-    const gfx::Transform& parent_matrix) {
-  // For every layer that has non-zero scroll_delta, we have to compute a
-  // transform that can undo the scroll_delta translation. In particular, we
-  // want this matrix to premultiply a fixed-position layer's parent_matrix, so
-  // we design this transform in three steps as follows. The steps described
-  // here apply from right-to-left, so Step 1 would be the right-most matrix:
-  //
-  //     Step 1. transform from target surface space to the exact space where
-  //           scroll_delta is actually applied.
-  //           -- this is inverse of the matrix in step 3
-  //     Step 2. undo the scroll_delta
-  //           -- this is just a translation by scroll_delta.
-  //     Step 3. transform back to target surface space.
-  //           -- this transform is the "partial_layer_origin_transform" =
-  //           (parent_matrix * scale(layer->pageScaleDelta()));
-  //
-  // These steps create a matrix that both start and end in targetSurfaceSpace.
-  // So this matrix can pre-multiply any fixed-position layer's draw_transform
-  // to undo the scroll_deltas -- as long as that fixed position layer is fixed
-  // onto the same render_target as this scrolling_layer.
-  //
-
-  gfx::Transform partial_layer_origin_transform = parent_matrix;
-  partial_layer_origin_transform.PreconcatTransform(
-      scrolling_layer->impl_transform());
-
-  gfx::Transform scroll_compensation_for_this_layer =
-      partial_layer_origin_transform;        // Step 3
-  scroll_compensation_for_this_layer.Translate(
-      scrolling_layer->scroll_delta().x(),
-      scrolling_layer->scroll_delta().y());  // Step 2
-
-  gfx::Transform inverse_partial_layer_origin_transform(
-      gfx::Transform::kSkipInitialization);
-  if (!partial_layer_origin_transform.GetInverse(
-          &inverse_partial_layer_origin_transform)) {
-    // TODO(shawnsingh): Either we need to handle uninvertible transforms
-    // here, or DCHECK that the transform is invertible.
-  }
-  scroll_compensation_for_this_layer.PreconcatTransform(
-      inverse_partial_layer_origin_transform);  // Step 1
-  return scroll_compensation_for_this_layer;
-}
-
-gfx::Transform ComputeScrollCompensationMatrixForChildren(
-    Layer* current_layer,
-    const gfx::Transform& current_parent_matrix,
-    const gfx::Transform& current_scroll_compensation) {
-  // The main thread (i.e. Layer) does not need to worry about scroll
-  // compensation.  So we can just return an identity matrix here.
-  return gfx::Transform();
-}
-
-gfx::Transform ComputeScrollCompensationMatrixForChildren(
-    LayerImpl* layer,
-    const gfx::Transform& parent_matrix,
-    const gfx::Transform& current_scroll_compensation_matrix) {
-  // "Total scroll compensation" is the transform needed to cancel out all
-  // scroll_delta translations that occurred since the nearest container layer,
-  // even if there are render_surfaces in-between.
-  //
-  // There are some edge cases to be aware of, that are not explicit in the
-  // code:
-  //  - A layer that is both a fixed-position and container should not be its
-  //  own container, instead, that means it is fixed to an ancestor, and is a
-  //  container for any fixed-position descendants.
-  //  - A layer that is a fixed-position container and has a render_surface
-  //  should behave the same as a container without a render_surface, the
-  //  render_surface is irrelevant in that case.
-  //  - A layer that does not have an explicit container is simply fixed to the
-  //  viewport.  (i.e. the root render_surface.)
-  //  - If the fixed-position layer has its own render_surface, then the
-  //  render_surface is the one who gets fixed.
-  //
-  // This function needs to be called AFTER layers create their own
-  // render_surfaces.
-  //
-
-  // Avoid the overheads (including stack allocation and matrix
-  // initialization/copy) if we know that the scroll compensation doesn't need
-  // to be reset or adjusted.
-  if (!layer->is_container_for_fixed_position_layers() &&
-      layer->scroll_delta().IsZero() && !layer->render_surface())
-    return current_scroll_compensation_matrix;
-
-  // Start as identity matrix.
-  gfx::Transform next_scroll_compensation_matrix;
-
-  // If this layer is not a container, then it inherits the existing scroll
-  // compensations.
-  if (!layer->is_container_for_fixed_position_layers())
-    next_scroll_compensation_matrix = current_scroll_compensation_matrix;
-
-  // If the current layer has a non-zero scroll_delta, then we should compute
-  // its local scrollCompensation and accumulate it to the
-  // next_scroll_compensation_matrix.
-  if (!layer->scroll_delta().IsZero()) {
-    gfx::Transform scroll_compensation_for_this_layer =
-        ComputeScrollCompensationForThisLayer(layer, parent_matrix);
-    next_scroll_compensation_matrix.PreconcatTransform(
-        scroll_compensation_for_this_layer);
-  }
-
-  // If the layer created its own render_surface, we have to adjust
-  // next_scroll_compensation_matrix.  The adjustment allows us to continue
-  // using the scrollCompensation on the next surface.
-  //  Step 1 (right-most in the math): transform from the new surface to the
-  //  original ancestor surface
-  //  Step 2: apply the scroll compensation
-  //  Step 3: transform back to the new surface.
-  if (layer->render_surface() &&
-      !next_scroll_compensation_matrix.IsIdentity()) {
-    gfx::Transform inverse_surface_draw_transform(
-        gfx::Transform::kSkipInitialization);
-    if (!layer->render_surface()->draw_transform().GetInverse(
-            &inverse_surface_draw_transform)) {
-      // TODO(shawnsingh): Either we need to handle uninvertible transforms
-      // here, or DCHECK that the transform is invertible.
-    }
-    next_scroll_compensation_matrix =
-        inverse_surface_draw_transform * next_scroll_compensation_matrix *
-        layer->render_surface()->draw_transform();
-  }
-
-  return next_scroll_compensation_matrix;
-}
-
-template <typename LayerType>
-static inline void CalculateContentsScale(LayerType* layer,
-                                          float contents_scale,
-                                          bool animating_transform_to_screen) {
-  layer->CalculateContentsScale(contents_scale,
-                                animating_transform_to_screen,
-                                &layer->draw_properties().contents_scale_x,
-                                &layer->draw_properties().contents_scale_y,
-                                &layer->draw_properties().content_bounds);
-
-  LayerType* mask_layer = layer->mask_layer();
-  if (mask_layer) {
-    mask_layer->CalculateContentsScale(
-        contents_scale,
+static inline void updateTilePrioritiesForLayer(LayerImpl* layer)
+{
+    layer->UpdateTilePriorities();
+
+    // Mask layers don't get this call, so explicitly update them so they can
+    // kick off tile rasterization.
+    if (layer->mask_layer())
+        layer->mask_layer()->UpdateTilePriorities();
+    if (layer->replica_layer() && layer->replica_layer()->mask_layer())
+      layer->replica_layer()->mask_layer()->UpdateTilePriorities();
+}
+
+static inline void updateTilePrioritiesForLayer(Layer* layer)
+{
+}
+
+template<typename LayerType>
+static bool subtreeShouldRenderToSeparateSurface(LayerType* layer, bool axisAlignedWithRespectToParent)
+{
+    //
+    // A layer and its descendants should render onto a new RenderSurfaceImpl if any of these rules hold:
+    //
+
+    // The root layer should always have a renderSurface.
+    if (isRootLayer(layer))
+        return true;
+
+    // If we force it.
+    if (layer->force_render_surface())
+        return true;
+
+    // If the layer uses a mask.
+    if (layer->mask_layer())
+        return true;
+
+    // If the layer has a reflection.
+    if (layer->replica_layer())
+        return true;
+
+    // If the layer uses a CSS filter.
+    if (!layer->filters().isEmpty() || !layer->background_filters().isEmpty() || layer->filter())
+        return true;
+
+    int numDescendantsThatDrawContent = layer->draw_properties().num_descendants_that_draw_content;
+
+    // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but it is
+    // treated as a 3D object by its parent (i.e. parent does preserve-3d).
+    if (layerIsInExisting3DRenderingContext(layer) && !layer->preserves_3d() && numDescendantsThatDrawContent > 0) {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface flattening");
+        return true;
+    }
+
+    // If the layer clips its descendants but it is not axis-aligned with respect to its parent.
+    bool layerClipsExternalContent = layerClipsSubtree(layer) || layer->HasDelegatedContent();
+    if (layerClipsExternalContent && !axisAlignedWithRespectToParent && !layer->draw_properties().descendants_can_clip_selves)
+    {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface clipping");
+        return true;
+    }
+
+    // If the layer has some translucency and does not have a preserves-3d transform style.
+    // This condition only needs a render surface if two or more layers in the
+    // subtree overlap. But checking layer overlaps is unnecessarily costly so
+    // instead we conservatively create a surface whenever at least two layers
+    // draw content for this subtree.
+    bool atLeastTwoLayersInSubtreeDrawContent = numDescendantsThatDrawContent > 0 && (layer->DrawsContent() || numDescendantsThatDrawContent > 1);
+
+    if (layer->opacity() != 1.f && !layer->preserves_3d() && atLeastTwoLayersInSubtreeDrawContent) {
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface opacity");
+        return true;
+    }
+
+    return false;
+}
+
+gfx::Transform computeScrollCompensationForThisLayer(LayerImpl* scrollingLayer, const gfx::Transform& parentMatrix)
+{
+    // For every layer that has non-zero scrollDelta, we have to compute a transform that can undo the
+    // scrollDelta translation. In particular, we want this matrix to premultiply a fixed-position layer's
+    // parentMatrix, so we design this transform in three steps as follows. The steps described here apply
+    // from right-to-left, so Step 1 would be the right-most matrix:
+    //
+    //     Step 1. transform from target surface space to the exact space where scrollDelta is actually applied.
+    //           -- this is inverse of the matrix in step 3
+    //     Step 2. undo the scrollDelta
+    //           -- this is just a translation by scrollDelta.
+    //     Step 3. transform back to target surface space.
+    //           -- this transform is the "partialLayerOriginTransform" = (parentMatrix * scale(layer->pageScaleDelta()));
+    //
+    // These steps create a matrix that both start and end in targetSurfaceSpace. So this matrix can
+    // pre-multiply any fixed-position layer's drawTransform to undo the scrollDeltas -- as long as
+    // that fixed position layer is fixed onto the same renderTarget as this scrollingLayer.
+    //
+
+    gfx::Transform partialLayerOriginTransform = parentMatrix;
+    partialLayerOriginTransform.PreconcatTransform(scrollingLayer->impl_transform());
+
+    gfx::Transform scrollCompensationForThisLayer = partialLayerOriginTransform; // Step 3
+    scrollCompensationForThisLayer.Translate(scrollingLayer->scroll_delta().x(), scrollingLayer->scroll_delta().y()); // Step 2
+
+    gfx::Transform inversePartialLayerOriginTransform(gfx::Transform::kSkipInitialization);
+    if (!partialLayerOriginTransform.GetInverse(&inversePartialLayerOriginTransform)) {
+        // TODO(shawnsingh): Either we need to handle uninvertible transforms
+        // here, or DCHECK that the transform is invertible.
+    }
+    scrollCompensationForThisLayer.PreconcatTransform(inversePartialLayerOriginTransform); // Step 1
+    return scrollCompensationForThisLayer;
+}
+
+gfx::Transform computeScrollCompensationMatrixForChildren(Layer* current_layer, const gfx::Transform& currentParentMatrix, const gfx::Transform& currentScrollCompensation)
+{
+    // The main thread (i.e. Layer) does not need to worry about scroll compensation.
+    // So we can just return an identity matrix here.
+    return gfx::Transform();
+}
+
+gfx::Transform computeScrollCompensationMatrixForChildren(LayerImpl* layer, const gfx::Transform& parentMatrix, const gfx::Transform& currentScrollCompensationMatrix)
+{
+    // "Total scroll compensation" is the transform needed to cancel out all scrollDelta translations that
+    // occurred since the nearest container layer, even if there are renderSurfaces in-between.
+    //
+    // There are some edge cases to be aware of, that are not explicit in the code:
+    //  - A layer that is both a fixed-position and container should not be its own container, instead, that means
+    //    it is fixed to an ancestor, and is a container for any fixed-position descendants.
+    //  - A layer that is a fixed-position container and has a renderSurface should behave the same as a container
+    //    without a renderSurface, the renderSurface is irrelevant in that case.
+    //  - A layer that does not have an explicit container is simply fixed to the viewport.
+    //    (i.e. the root renderSurface.)
+    //  - If the fixed-position layer has its own renderSurface, then the renderSurface is
+    //    the one who gets fixed.
+    //
+    // This function needs to be called AFTER layers create their own renderSurfaces.
+    //
+
+    // Avoid the overheads (including stack allocation and matrix initialization/copy) if we know that the scroll compensation doesn't need to be reset or adjusted.
+    if (!layer->is_container_for_fixed_position_layers() && layer->scroll_delta().IsZero() && !layer->render_surface())
+        return currentScrollCompensationMatrix;
+
+    // Start as identity matrix.
+    gfx::Transform nextScrollCompensationMatrix;
+
+    // If this layer is not a container, then it inherits the existing scroll compensations.
+    if (!layer->is_container_for_fixed_position_layers())
+        nextScrollCompensationMatrix = currentScrollCompensationMatrix;
+
+    // If the current layer has a non-zero scrollDelta, then we should compute its local scrollCompensation
+    // and accumulate it to the nextScrollCompensationMatrix.
+    if (!layer->scroll_delta().IsZero()) {
+        gfx::Transform scrollCompensationForThisLayer = computeScrollCompensationForThisLayer(layer, parentMatrix);
+        nextScrollCompensationMatrix.PreconcatTransform(scrollCompensationForThisLayer);
+    }
+
+    // If the layer created its own renderSurface, we have to adjust nextScrollCompensationMatrix.
+    // The adjustment allows us to continue using the scrollCompensation on the next surface.
+    //  Step 1 (right-most in the math): transform from the new surface to the original ancestor surface
+    //  Step 2: apply the scroll compensation
+    //  Step 3: transform back to the new surface.
+    if (layer->render_surface() && !nextScrollCompensationMatrix.IsIdentity()) {
+        gfx::Transform inverseSurfaceDrawTransform(gfx::Transform::kSkipInitialization);
+        if (!layer->render_surface()->draw_transform().GetInverse(&inverseSurfaceDrawTransform)) {
+            // TODO(shawnsingh): Either we need to handle uninvertible transforms
+            // here, or DCHECK that the transform is invertible.
+        }
+        nextScrollCompensationMatrix = inverseSurfaceDrawTransform * nextScrollCompensationMatrix * layer->render_surface()->draw_transform();
+    }
+
+    return nextScrollCompensationMatrix;
+}
+
+template<typename LayerType>
+static inline void CalculateContentsScale(LayerType* layer, float contentsScale, bool animating_transform_to_screen)
+{
+    layer->CalculateContentsScale(
+        contentsScale,
         animating_transform_to_screen,
-        &mask_layer->draw_properties().contents_scale_x,
-        &mask_layer->draw_properties().contents_scale_y,
-        &mask_layer->draw_properties().content_bounds);
-  }
-
-  LayerType* replica_mask_layer =
-      layer->replica_layer() ? layer->replica_layer()->mask_layer() : NULL;
-  if (replica_mask_layer) {
-    replica_mask_layer->CalculateContentsScale(
-        contents_scale,
-        animating_transform_to_screen,
-        &replica_mask_layer->draw_properties().contents_scale_x,
-        &replica_mask_layer->draw_properties().contents_scale_y,
-        &replica_mask_layer->draw_properties().content_bounds);
-  }
-}
-
-static inline void UpdateLayerContentsScale(
-    LayerImpl* layer,
-    const gfx::Transform& combined_transform,
-    float device_scale_factor,
-    float page_scale_factor,
-    bool animating_transform_to_screen) {
-  gfx::Vector2dF transform_scale = MathUtil::ComputeTransform2dScaleComponents(
-      combined_transform, device_scale_factor * page_scale_factor);
-  float contents_scale = std::max(transform_scale.x(), transform_scale.y());
-  CalculateContentsScale(layer, contents_scale, animating_transform_to_screen);
-}
-
-static inline void UpdateLayerContentsScale(
-    Layer* layer,
-    const gfx::Transform& combined_transform,
-    float device_scale_factor,
-    float page_scale_factor,
-    bool animating_transform_to_screen) {
-  float raster_scale = layer->raster_scale();
-
-  if (layer->automatically_compute_raster_scale()) {
-    gfx::Vector2dF transform_scale =
-        MathUtil::ComputeTransform2dScaleComponents(combined_transform, 0.f);
-    float combined_scale = std::max(transform_scale.x(), transform_scale.y());
-    float ideal_raster_scale = combined_scale / device_scale_factor;
+        &layer->draw_properties().contents_scale_x,
+        &layer->draw_properties().contents_scale_y,
+        &layer->draw_properties().content_bounds);
+
+    LayerType* maskLayer = layer->mask_layer();
+    if (maskLayer)
+    {
+        maskLayer->CalculateContentsScale(
+            contentsScale,
+            animating_transform_to_screen,
+            &maskLayer->draw_properties().contents_scale_x,
+            &maskLayer->draw_properties().contents_scale_y,
+            &maskLayer->draw_properties().content_bounds);
+    }
+
+    LayerType* replicaMaskLayer = layer->replica_layer() ? layer->replica_layer()->mask_layer() : 0;
+    if (replicaMaskLayer)
+    {
+        replicaMaskLayer->CalculateContentsScale(
+            contentsScale,
+            animating_transform_to_screen,
+            &replicaMaskLayer->draw_properties().contents_scale_x,
+            &replicaMaskLayer->draw_properties().contents_scale_y,
+            &replicaMaskLayer->draw_properties().content_bounds);
+    }
+}
+
+static inline void updateLayerContentsScale(LayerImpl* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animating_transform_to_screen)
+{
+    gfx::Vector2dF transformScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
+    float contentsScale = std::max(transformScale.x(), transformScale.y());
+    CalculateContentsScale(layer, contentsScale, animating_transform_to_screen);
+}
+
+static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animating_transform_to_screen)
+{
+    float rasterScale = layer->raster_scale();
+
+    if (layer->automatically_compute_raster_scale()) {
+        gfx::Vector2dF transformScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, 0.f);
+        float combinedScale = std::max(transformScale.x(), transformScale.y());
+        float idealRasterScale = combinedScale / deviceScaleFactor;
+        if (!layer->bounds_contain_page_scale())
+            idealRasterScale /= pageScaleFactor;
+
+        bool needToSetRasterScale = !rasterScale;
+
+        // If we've previously saved a rasterScale but the ideal changes, things are unpredictable and we should just use 1.
+        if (rasterScale && rasterScale != 1.f && idealRasterScale != rasterScale) {
+            idealRasterScale = 1.f;
+            needToSetRasterScale = true;
+        }
+
+        if (needToSetRasterScale) {
+            bool useAndSaveIdealScale = idealRasterScale >= 1.f && !animating_transform_to_screen;
+            if (useAndSaveIdealScale) {
+                rasterScale = idealRasterScale;
+                layer->SetRasterScale(rasterScale);
+            }
+        }
+    }
+
+    if (!rasterScale)
+        rasterScale = 1.f;
+
+    float contentsScale = rasterScale * deviceScaleFactor;
     if (!layer->bounds_contain_page_scale())
-      ideal_raster_scale /= page_scale_factor;
-
-    bool need_to_set_raster_scale = !raster_scale;
-
-    // If we've previously saved a raster_scale but the ideal changes, things
-    // are unpredictable and we should just use 1.
-    if (raster_scale && raster_scale != 1.f &&
-        ideal_raster_scale != raster_scale) {
-      ideal_raster_scale = 1.f;
-      need_to_set_raster_scale = true;
-    }
-
-    if (need_to_set_raster_scale) {
-      bool use_and_save_ideal_scale =
-          ideal_raster_scale >= 1.f && !animating_transform_to_screen;
-      if (use_and_save_ideal_scale) {
-        raster_scale = ideal_raster_scale;
-        layer->SetRasterScale(raster_scale);
-      }
-    }
-  }
-
-  if (!raster_scale)
-    raster_scale = 1.f;
-
-  float contents_scale = raster_scale * device_scale_factor;
-  if (!layer->bounds_contain_page_scale())
-    contents_scale *= page_scale_factor;
-
-  CalculateContentsScale(layer, contents_scale, animating_transform_to_screen);
-}
-
-template <typename LayerType, typename LayerList>
-static inline void RemoveSurfaceForEarlyExit(
-    LayerType* layer_to_remove,
-    LayerList& render_surface_layer_list) {
-  DCHECK(layer_to_remove->render_surface());
-  // Technically, we know that the layer we want to remove should be
-  // at the back of the render_surface_layer_list. However, we have had
-  // bugs before that added unnecessary layers here
-  // (https://bugs.webkit.org/show_bug.cgi?id=74147), but that causes
-  // things to crash. So here we proactively remove any additional
-  // layers from the end of the list.
-  while (render_surface_layer_list->back() != layer_to_remove) {
-    render_surface_layer_list->back()->ClearRenderSurface();
-    render_surface_layer_list->pop_back();
-  }
-  DCHECK_EQ(render_surface_layer_list->back(), layer_to_remove);
-  render_surface_layer_list->pop_back();
-  layer_to_remove->ClearRenderSurface();
+        contentsScale *= pageScaleFactor;
+
+    CalculateContentsScale(layer, contentsScale, animating_transform_to_screen);
+}
+
+template<typename LayerType, typename LayerList>
+static inline void removeSurfaceForEarlyExit(LayerType* layerToRemove, LayerList& renderSurfaceLayerList)
+{
+    DCHECK(layerToRemove->render_surface());
+    // Technically, we know that the layer we want to remove should be
+    // at the back of the renderSurfaceLayerList. However, we have had
+    // bugs before that added unnecessary layers here
+    // (https://bugs.webkit.org/show_bug.cgi?id=74147), but that causes
+    // things to crash. So here we proactively remove any additional
+    // layers from the end of the list.
+    while (renderSurfaceLayerList.back() != layerToRemove) {
+        renderSurfaceLayerList.back()->ClearRenderSurface();
+        renderSurfaceLayerList.pop_back();
+    }
+    DCHECK(renderSurfaceLayerList.back() == layerToRemove);
+    renderSurfaceLayerList.pop_back();
+    layerToRemove->ClearRenderSurface();
 }
 
 // Recursively walks the layer tree to compute any information that is needed
 // before doing the main recursion.
-template <typename LayerType>
-static void PreCalculateMetaInformation(LayerType* layer) {
-  if (layer->HasDelegatedContent()) {
-    // Layers with delegated content need to be treated as if they have as many
-    // children as the number of layers they own delegated quads for. Since we
-    // don't know this number right now, we choose one that acts like infinity
-    // for our purposes.
-    layer->draw_properties().num_descendants_that_draw_content = 1000;
-    layer->draw_properties().descendants_can_clip_selves = false;
-    return;
-  }
-
-  int num_descendants_that_draw_content = 0;
-  bool descendants_can_clip_selves = true;
-  bool sublayer_transform_prevents_clip =
-      !layer->sublayer_transform().IsPositiveScaleOrTranslation();
-
-  for (size_t i = 0; i < layer->children().size(); ++i) {
-    LayerType* child_layer = layer->children()[i];
-    PreCalculateMetaInformation<LayerType>(child_layer);
-
-    num_descendants_that_draw_content += child_layer->DrawsContent() ? 1 : 0;
-    num_descendants_that_draw_content +=
-        child_layer->draw_properties().num_descendants_that_draw_content;
-
-    if ((child_layer->DrawsContent() && !child_layer->CanClipSelf()) ||
-        !child_layer->draw_properties().descendants_can_clip_selves ||
-        sublayer_transform_prevents_clip ||
-        !child_layer->transform().IsPositiveScaleOrTranslation())
-      descendants_can_clip_selves = false;
-  }
-
-  layer->draw_properties().num_descendants_that_draw_content =
-      num_descendants_that_draw_content;
-  layer->draw_properties().descendants_can_clip_selves =
-      descendants_can_clip_selves;
-}
-
-static void RoundTranslationComponents(gfx::Transform* transform) {
-  transform->matrix().
-      setDouble(0, 3, MathUtil::Round(transform->matrix().getDouble(0, 3)));
-  transform->matrix().
-      setDouble(1, 3, MathUtil::Round(transform->matrix().getDouble(1, 3)));
-}
-
-// Recursively walks the layer tree starting at the given node and computes all
-// the necessary transformations, clipRects, render surfaces, etc.
-template <typename LayerType, typename LayerList, typename RenderSurfaceType>
-static void CalculateDrawPropertiesInternal(
-    LayerType* layer,
-    const gfx::Transform& parent_matrix,
-    const gfx::Transform& full_hierarchy_matrix,
-    const gfx::Transform& current_scroll_compensation_matrix,
-    gfx::Rect clip_rect_from_ancestor,
-    gfx::Rect clip_rect_from_ancestor_in_descendant_space,
-    bool ancestor_clips_subtree,
-    RenderSurfaceType* nearest_ancestor_that_moves_pixels,
-    LayerList* render_surface_layer_list,
-    LayerList* layer_list,
-    LayerSorter* layer_sorter,
-    int max_texture_size,
-    float device_scale_factor,
-    float page_scale_factor,
-    bool subtree_can_use_lcd_text,
-    gfx::Rect* drawable_content_rect_of_subtree,
-    bool update_tile_priorities) {
-  // This function computes the new matrix transformations recursively for this
-  // layer and all its descendants. It also computes the appropriate render
-  // surfaces.
-  // Some important points to remember:
-  //
-  // 0. Here, transforms are notated in Matrix x Vector order, and in words we
-  // describe what the transform does from left to right.
-  //
-  // 1. In our terminology, the "layer origin" refers to the top-left corner of
-  // a layer, and the positive Y-axis points downwards. This interpretation is
-  // valid because the orthographic projection applied at draw time flips the Y
-  // axis appropriately.
-  //
-  // 2. The anchor point, when given as a PointF object, is specified in "unit
-  // layer space", where the bounds of the layer map to [0, 1]. However, as a
-  // Transform object, the transform to the anchor point is specified in "layer
-  // space", where the bounds of the layer map to [bounds.width(),
-  // bounds.height()].
-  //
-  // 3. Definition of various transforms used:
-  //        M[parent] is the parent matrix, with respect to the nearest render
-  //        surface, passed down recursively.
-  //
-  //        M[root] is the full hierarchy, with respect to the root, passed down
-  //        recursively.
-  //
-  //        Tr[origin] is the translation matrix from the parent's origin to
-  //        this layer's origin.
-  //
-  //        Tr[origin2anchor] is the translation from the layer's origin to its
-  //        anchor point
-  //
-  //        Tr[origin2center] is the translation from the layer's origin to its
-  //        center
-  //
-  //        M[layer] is the layer's matrix (applied at the anchor point)
-  //
-  //        M[sublayer] is the layer's sublayer transform (also applied at the
-  //        layer's anchor point)
-  //
-  //        S[layer2content] is the ratio of a layer's ContentBounds() to its
-  //        Bounds().
-  //
-  //    Some composite transforms can help in understanding the sequence of
-  //    transforms:
-  //        compositeLayerTransform = Tr[origin2anchor] * M[layer] *
-  //        Tr[origin2anchor].inverse()
-  //
-  //        compositeSublayerTransform = Tr[origin2anchor] * M[sublayer] *
-  //        Tr[origin2anchor].inverse()
-  //
-  // 4. When a layer (or render surface) is drawn, it is drawn into a "target
-  // render surface". Therefore the draw transform does not necessarily
-  // transform from screen space to local layer space. Instead, the draw
-  // transform is the transform between the "target render surface space" and
-  // local layer space. Note that render surfaces, except for the root, also
-  // draw themselves into a different target render surface, and so their draw
-  // transform and origin transforms are also described with respect to the
-  // target.
-  //
-  // Using these definitions, then:
-  //
-  // The draw transform for the layer is:
-  //        M[draw] = M[parent] * Tr[origin] * compositeLayerTransform *
-  //            S[layer2content] = M[parent] * Tr[layer->Position() + anchor] *
-  //            M[layer] * Tr[anchor2origin] * S[layer2content]
-  //
-  //        Interpreting the math left-to-right, this transforms from the
-  //        layer's render surface to the origin of the layer in content space.
-  //
-  // The screen space transform is:
-  //        M[screenspace] = M[root] * Tr[origin] * compositeLayerTransform *
-  //            S[layer2content]
-  //                       = M[root] * Tr[layer->Position() + anchor] * M[layer]
-  //                           * Tr[anchor2origin] * S[layer2content]
-  //
-  //        Interpreting the math left-to-right, this transforms from the root
-  //        render surface's content space to the origin of the layer in content
-  //        space.
-  //
-  // The transform hierarchy that is passed on to children (i.e. the child's
-  // parent_matrix) is:
-  //        M[parent]_for_child = M[parent] * Tr[origin] *
-  //            compositeLayerTransform * compositeSublayerTransform
-  //                            = M[parent] * Tr[layer->Position() + anchor] *
-  //                                M[layer] * Tr[anchor2origin] *
-  //                                compositeSublayerTransform
-  //
-  //        and a similar matrix for the full hierarchy with respect to the
-  //        root.
-  //
-  // Finally, note that the final matrix used by the shader for the layer is P *
-  // M[draw] * S . This final product is computed in drawTexturedQuad(), where:
-  //        P is the projection matrix
-  //        S is the scale adjustment (to scale up a canonical quad to the
-  //            layer's size)
-  //
-  // When a render surface has a replica layer, that layer's transform is used
-  // to draw a second copy of the surface.  gfx::Transforms named here are
-  // relative to the surface, unless they specify they are relative to the
-  // replica layer.
-  //
-  // We will denote a scale by device scale S[deviceScale]
-  //
-  // The render surface draw transform to its target surface origin is:
-  //        M[surfaceDraw] = M[owningLayer->Draw]
-  //
-  // The render surface origin transform to its the root (screen space) origin
-  // is:
-  //        M[surface2root] =  M[owningLayer->screenspace] *
-  //            S[deviceScale].inverse()
-  //
-  // The replica draw transform to its target surface origin is:
-  //        M[replicaDraw] = S[deviceScale] * M[surfaceDraw] *
-  //            Tr[replica->Position() + replica->anchor()] * Tr[replica] *
-  //            Tr[origin2anchor].inverse() * S[contents_scale].inverse()
-  //
-  // The replica draw transform to the root (screen space) origin is:
-  //        M[replica2root] = M[surface2root] * Tr[replica->Position()] *
-  //            Tr[replica] * Tr[origin2anchor].inverse()
-  //
-
-  // If we early-exit anywhere in this function, the drawableContentRect of this
-  // subtree should be considered empty.
-  *drawable_content_rect_of_subtree = gfx::Rect();
-
-  // The root layer cannot skip calcDrawProperties.
-  if (!IsRootLayer(layer) && SubtreeShouldBeSkipped(layer))
-    return;
-
-  // As this function proceeds, these are the properties for the current
-  // layer that actually get computed. To avoid unnecessary copies
-  // (particularly for matrices), we do computations directly on these values
-  // when possible.
-  DrawProperties<LayerType, RenderSurfaceType>& layer_draw_properties =
-      layer->draw_properties();
-
-  gfx::Rect clip_rect_for_subtree;
-  bool subtree_should_be_clipped = false;
-
-  // This value is cached on the stack so that we don't have to inverse-project
-  // the surface's clipRect redundantly for every layer. This value is the
-  // same as the surface's clipRect, except that instead of being described
-  // in the target surface space (i.e. the ancestor surface space), it is
-  // described in the current surface space.
-  gfx::Rect clip_rect_for_subtree_in_descendant_space;
-
-  float accumulated_draw_opacity = layer->opacity();
-  bool animating_opacity_to_target = layer->OpacityIsAnimating();
-  bool animating_opacity_to_screen = animating_opacity_to_target;
-  if (layer->parent()) {
-    accumulated_draw_opacity *= layer->parent()->draw_opacity();
-    animating_opacity_to_target |= layer->parent()->draw_opacity_is_animating();
-    animating_opacity_to_screen |=
-        layer->parent()->screen_space_opacity_is_animating();
-  }
-
-  bool animating_transform_to_target = layer->TransformIsAnimating();
-  bool animating_transform_to_screen = animating_transform_to_target;
-  if (layer->parent()) {
-    animating_transform_to_target |=
-        layer->parent()->draw_transform_is_animating();
-    animating_transform_to_screen |=
-        layer->parent()->screen_space_transform_is_animating();
-  }
-
-  gfx::Size bounds = layer->bounds();
-  gfx::PointF anchor_point = layer->anchor_point();
-  gfx::PointF position = layer->position() - layer->scroll_delta();
-
-  gfx::Transform combined_transform = parent_matrix;
-  if (!layer->transform().IsIdentity()) {
-    // LT = Tr[origin] * Tr[origin2anchor]
-    combined_transform.Translate3d(
-        position.x() + anchor_point.x() * bounds.width(),
-        position.y() + anchor_point.y() * bounds.height(),
-        layer->anchor_point_z());
-    // LT = Tr[origin] * Tr[origin2anchor] * M[layer]
-    combined_transform.PreconcatTransform(layer->transform());
-    // LT = Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2origin]
-    combined_transform.Translate3d(-anchor_point.x() * bounds.width(),
-                                   -anchor_point.y() * bounds.height(),
-                                   -layer->anchor_point_z());
-  } else {
-    combined_transform.Translate(position.x(), position.y());
-  }
-
-  // The layer's contentsSize is determined from the combined_transform, which
-  // then informs the layer's draw_transform.
-  UpdateLayerContentsScale(layer,
-                           combined_transform,
-                           device_scale_factor,
-                           page_scale_factor,
-                           animating_transform_to_screen);
-
-  // If there is a transformation from the impl thread then it should be at
-  // the start of the combined_transform, but we don't want it to affect the
-  // computation of contents_scale above.
-  // Note carefully: this is Concat, not Preconcat (implTransform *
-  // combined_transform).
-  combined_transform.ConcatTransform(layer->impl_transform());
-
-  if (!animating_transform_to_target && layer->scrollable() &&
-      combined_transform.IsScaleOrTranslation()) {
-    // Align the scrollable layer's position to screen space pixels to avoid
-    // blurriness.  To avoid side-effects, do this only if the transform is
-    // simple.
-    RoundTranslationComponents(&combined_transform);
-  }
-
-  if (layer->fixed_to_container_layer()) {
-    // Special case: this layer is a composited fixed-position layer; we need to
-    // explicitly compensate for all ancestors' nonzero scroll_deltas to keep
-    // this layer fixed correctly.
-    // Note carefully: this is Concat, not Preconcat
-    // (current_scroll_compensation * combined_transform).
-    combined_transform.ConcatTransform(current_scroll_compensation_matrix);
-  }
-
-  // The draw_transform that gets computed below is effectively the layer's
-  // draw_transform, unless the layer itself creates a render_surface. In that
-  // case, the render_surface re-parents the transforms.
-  layer_draw_properties.target_space_transform = combined_transform;
-  // M[draw] = M[parent] * LT * S[layer2content]
-  layer_draw_properties.target_space_transform.Scale
-      (1.f / layer->contents_scale_x(), 1.f / layer->contents_scale_y());
-
-  // layerScreenSpaceTransform represents the transform between root layer's
-  // "screen space" and local content space.
-  layer_draw_properties.screen_space_transform = full_hierarchy_matrix;
-  if (!layer->preserves_3d())
-    layer_draw_properties.screen_space_transform.FlattenTo2d();
-  layer_draw_properties.screen_space_transform.PreconcatTransform
-      (layer_draw_properties.target_space_transform);
-
-  // Adjusting text AA method during animation may cause repaints, which in-turn
-  // causes jank.
-  bool adjust_text_aa =
-      !animating_opacity_to_screen && !animating_transform_to_screen;
-  // To avoid color fringing, LCD text should only be used on opaque layers with
-  // just integral translation.
-  bool layer_can_use_lcd_text =
-      subtree_can_use_lcd_text && (accumulated_draw_opacity == 1.f) &&
-      layer_draw_properties.target_space_transform.
-          IsIdentityOrIntegerTranslation();
-
-  gfx::RectF content_rect(gfx::PointF(), layer->content_bounds());
-
-  // full_hierarchy_matrix is the matrix that transforms objects between screen
-  // space (except projection matrix) and the most recent RenderSurfaceImpl's
-  // space.  next_hierarchy_matrix will only change if this layer uses a new
-  // RenderSurfaceImpl, otherwise remains the same.
-  gfx::Transform next_hierarchy_matrix = full_hierarchy_matrix;
-  gfx::Transform sublayer_matrix;
-
-  gfx::Vector2dF render_surface_sublayer_scale =
-      MathUtil::ComputeTransform2dScaleComponents(
-          combined_transform, device_scale_factor * page_scale_factor);
-
-  if (SubtreeShouldRenderToSeparateSurface(
-          layer, combined_transform.IsScaleOrTranslation())) {
-    // Check back-face visibility before continuing with this surface and its
-    // subtree
-    if (!layer->double_sided() && TransformToParentIsKnown(layer) &&
-        IsSurfaceBackFaceVisible(layer, combined_transform))
-      return;
-
-    if (!layer->render_surface())
-      layer->CreateRenderSurface();
-
-    RenderSurfaceType* render_surface = layer->render_surface();
-    render_surface->ClearLayerLists();
-
-    // The owning layer's draw transform has a scale from content to layer
-    // space which we do not want; so here we use the combined_transform
-    // instead of the draw_transform. However, we do need to add a different
-    // scale factor that accounts for the surface's pixel dimensions.
-    combined_transform.Scale(1.0 / render_surface_sublayer_scale.x(),
-                             1.0 / render_surface_sublayer_scale.y());
-    render_surface->SetDrawTransform(combined_transform);
-
-    // The owning layer's transform was re-parented by the surface, so the
-    // layer's new draw_transform only needs to scale the layer to surface
-    // space.
-    layer_draw_properties.target_space_transform.MakeIdentity();
-    layer_draw_properties.target_space_transform.
-        Scale(render_surface_sublayer_scale.x() / layer->contents_scale_x(),
-              render_surface_sublayer_scale.y() / layer->contents_scale_y());
-
-    // Inside the surface's subtree, we scale everything to the owning layer's
-    // scale.  The sublayer matrix transforms layer rects into target surface
-    // content space.
-    DCHECK(sublayer_matrix.IsIdentity());
-    sublayer_matrix.Scale(render_surface_sublayer_scale.x(),
-                          render_surface_sublayer_scale.y());
-
-    // The opacity value is moved from the layer to its surface, so that the
-    // entire subtree properly inherits opacity.
-    render_surface->SetDrawOpacity(accumulated_draw_opacity);
-    render_surface->SetDrawOpacityIsAnimating(animating_opacity_to_target);
-    animating_opacity_to_target = false;
-    layer_draw_properties.opacity = 1.f;
-    layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
-    layer_draw_properties.screen_space_opacity_is_animating =
-        animating_opacity_to_screen;
-
-    render_surface->SetTargetSurfaceTransformsAreAnimating(
-        animating_transform_to_target);
-    render_surface->SetScreenSpaceTransformsAreAnimating(
-        animating_transform_to_screen);
-    animating_transform_to_target = false;
-    layer_draw_properties.target_space_transform_is_animating =
-        animating_transform_to_target;
-    layer_draw_properties.screen_space_transform_is_animating =
-        animating_transform_to_screen;
-
-    // Update the aggregate hierarchy matrix to include the transform of the
-    // newly created RenderSurfaceImpl.
-    next_hierarchy_matrix.PreconcatTransform(render_surface->draw_transform());
-
-    // The new render_surface here will correctly clip the entire subtree. So,
-    // we do not need to continue propagating the clipping state further down
-    // the tree. This way, we can avoid transforming clipRects from ancestor
-    // target surface space to current target surface space that could cause
-    // more w < 0 headaches.
-    subtree_should_be_clipped = false;
-
-    if (layer->mask_layer()) {
-      DrawProperties<LayerType, RenderSurfaceType>& mask_layer_draw_properties =
-          layer->mask_layer()->draw_properties();
-      mask_layer_draw_properties.render_target = layer;
-      mask_layer_draw_properties.visible_content_rect =
-          gfx::Rect(gfx::Point(), layer->content_bounds());
-    }
-
-    if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
-      DrawProperties<LayerType, RenderSurfaceType>&
-      replica_mask_draw_properties =
-          layer->replica_layer()->mask_layer()->draw_properties();
-      replica_mask_draw_properties.render_target = layer;
-      replica_mask_draw_properties.visible_content_rect =
-          gfx::Rect(gfx::Point(), layer->content_bounds());
-    }
-
-    // TODO(senorblanco): make this smarter for the SkImageFilter case (check
-    // for pixel-moving filters)
-    if (layer->filters().hasFilterThatMovesPixels() || layer->filter())
-      nearest_ancestor_that_moves_pixels = render_surface;
-
-    // The render surface clipRect is expressed in the space where this surface
-    // draws, i.e. the same space as clip_rect_from_ancestor.
-    render_surface->SetIsClipped(ancestor_clips_subtree);
-    if (ancestor_clips_subtree) {
-      render_surface->SetClipRect(clip_rect_from_ancestor);
-
-      gfx::Transform inverse_surface_draw_transform(
-          gfx::Transform::kSkipInitialization);
-      if (!render_surface->draw_transform().GetInverse(
-              &inverse_surface_draw_transform)) {
-        // TODO(shawnsingh): Either we need to handle uninvertible transforms
-        // here, or DCHECK that the transform is invertible.
-      }
-      clip_rect_for_subtree_in_descendant_space =
-          gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
-              inverse_surface_draw_transform, render_surface->clip_rect()));
+template<typename LayerType>
+static void preCalculateMetaInformation(LayerType* layer)
+{
+    if (layer->HasDelegatedContent()) {
+        // Layers with delegated content need to be treated as if they have as many children as the number
+        // of layers they own delegated quads for. Since we don't know this number right now, we choose
+        // one that acts like infinity for our purposes.
+        layer->draw_properties().num_descendants_that_draw_content = 1000;
+        layer->draw_properties().descendants_can_clip_selves = false;
+        return;
+    }
+
+    int numDescendantsThatDrawContent = 0;
+    bool descendantsCanClipSelves = true;
+    bool sublayerTransformPreventsClip = !layer->sublayer_transform().IsPositiveScaleOrTranslation();
+
+    for (size_t i = 0; i < layer->children().size(); ++i) {
+        LayerType* childLayer = layer->children()[i];
+        preCalculateMetaInformation<LayerType>(childLayer);
+
+        numDescendantsThatDrawContent += childLayer->DrawsContent() ? 1 : 0;
+        numDescendantsThatDrawContent += childLayer->draw_properties().num_descendants_that_draw_content;
+
+        if ((childLayer->DrawsContent() && !childLayer->CanClipSelf()) ||
+            !childLayer->draw_properties().descendants_can_clip_selves ||
+            sublayerTransformPreventsClip ||
+            !childLayer->transform().IsPositiveScaleOrTranslation())
+            descendantsCanClipSelves = false;
+    }
+
+    layer->draw_properties().num_descendants_that_draw_content = numDescendantsThatDrawContent;
+    layer->draw_properties().descendants_can_clip_selves = descendantsCanClipSelves;
+}
+
+static void roundTranslationComponents(gfx::Transform* transform)
+{
+    transform->matrix().setDouble(0, 3, MathUtil::Round(transform->matrix().getDouble(0, 3)));
+    transform->matrix().setDouble(1, 3, MathUtil::Round(transform->matrix().getDouble(1, 3)));
+}
+
+// Recursively walks the layer tree starting at the given node and computes all the
+// necessary transformations, clipRects, render surfaces, etc.
+template<typename LayerType, typename LayerList, typename RenderSurfaceType>
+static void calculateDrawPropertiesInternal(LayerType* layer, const gfx::Transform& parentMatrix,
+    const gfx::Transform& fullHierarchyMatrix, const gfx::Transform& currentScrollCompensationMatrix,
+    const gfx::Rect& clipRectFromAncestor, const gfx::Rect& clipRectFromAncestorInDescendantSpace, bool ancestorClipsSubtree,
+    RenderSurfaceType* nearestAncestorThatMovesPixels, LayerList& renderSurfaceLayerList, LayerList& layerList,
+    LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, float pageScaleFactor, bool subtreeCanUseLCDText,
+    gfx::Rect& drawableContentRectOfSubtree, bool updateTilePriorities)
+{
+    // This function computes the new matrix transformations recursively for this
+    // layer and all its descendants. It also computes the appropriate render surfaces.
+    // Some important points to remember:
+    //
+    // 0. Here, transforms are notated in Matrix x Vector order, and in words we describe what
+    //    the transform does from left to right.
+    //
+    // 1. In our terminology, the "layer origin" refers to the top-left corner of a layer, and the
+    //    positive Y-axis points downwards. This interpretation is valid because the orthographic
+    //    projection applied at draw time flips the Y axis appropriately.
+    //
+    // 2. The anchor point, when given as a PointF object, is specified in "unit layer space",
+    //    where the bounds of the layer map to [0, 1]. However, as a Transform object,
+    //    the transform to the anchor point is specified in "layer space", where the bounds
+    //    of the layer map to [bounds.width(), bounds.height()].
+    //
+    // 3. Definition of various transforms used:
+    //        M[parent] is the parent matrix, with respect to the nearest render surface, passed down recursively.
+    //        M[root] is the full hierarchy, with respect to the root, passed down recursively.
+    //        Tr[origin] is the translation matrix from the parent's origin to this layer's origin.
+    //        Tr[origin2anchor] is the translation from the layer's origin to its anchor point
+    //        Tr[origin2center] is the translation from the layer's origin to its center
+    //        M[layer] is the layer's matrix (applied at the anchor point)
+    //        M[sublayer] is the layer's sublayer transform (also applied at the layer's anchor point)
+    //        S[layer2content] is the ratio of a layer's ContentBounds() to its Bounds().
+    //
+    //    Some composite transforms can help in understanding the sequence of transforms:
+    //        compositeLayerTransform = Tr[origin2anchor] * M[layer] * Tr[origin2anchor].inverse()
+    //        compositeSublayerTransform = Tr[origin2anchor] * M[sublayer] * Tr[origin2anchor].inverse()
+    //
+    // 4. When a layer (or render surface) is drawn, it is drawn into a "target render surface". Therefore the draw
+    //    transform does not necessarily transform from screen space to local layer space. Instead, the draw transform
+    //    is the transform between the "target render surface space" and local layer space. Note that render surfaces,
+    //    except for the root, also draw themselves into a different target render surface, and so their draw
+    //    transform and origin transforms are also described with respect to the target.
+    //
+    // Using these definitions, then:
+    //
+    // The draw transform for the layer is:
+    //        M[draw] = M[parent] * Tr[origin] * compositeLayerTransform * S[layer2content]
+    //                = M[parent] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
+    //
+    //        Interpreting the math left-to-right, this transforms from the layer's render surface to the origin of the layer in content space.
+    //
+    // The screen space transform is:
+    //        M[screenspace] = M[root] * Tr[origin] * compositeLayerTransform * S[layer2content]
+    //                       = M[root] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
+    //
+    //        Interpreting the math left-to-right, this transforms from the root render surface's content space to the origin of the layer in content space.
+    //
+    // The transform hierarchy that is passed on to children (i.e. the child's parentMatrix) is:
+    //        M[parent]_for_child = M[parent] * Tr[origin] * compositeLayerTransform * compositeSublayerTransform
+    //                            = M[parent] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * compositeSublayerTransform
+    //
+    //        and a similar matrix for the full hierarchy with respect to the root.
+    //
+    // Finally, note that the final matrix used by the shader for the layer is P * M[draw] * S . This final product
+    // is computed in drawTexturedQuad(), where:
+    //        P is the projection matrix
+    //        S is the scale adjustment (to scale up a canonical quad to the layer's size)
+    //
+    // When a render surface has a replica layer, that layer's transform is used to draw a second copy of the surface.
+    // gfx::Transforms named here are relative to the surface, unless they specify they are relative to the replica layer.
+    //
+    // We will denote a scale by device scale S[deviceScale]
+    //
+    // The render surface draw transform to its target surface origin is:
+    //        M[surfaceDraw] = M[owningLayer->Draw]
+    //
+    // The render surface origin transform to its the root (screen space) origin is:
+    //        M[surface2root] =  M[owningLayer->screenspace] * S[deviceScale].inverse()
+    //
+    // The replica draw transform to its target surface origin is:
+    //        M[replicaDraw] = S[deviceScale] * M[surfaceDraw] * Tr[replica->Position() + replica->anchor()] * Tr[replica] * Tr[origin2anchor].inverse() * S[contentsScale].inverse()
+    //
+    // The replica draw transform to the root (screen space) origin is:
+    //        M[replica2root] = M[surface2root] * Tr[replica->Position()] * Tr[replica] * Tr[origin2anchor].inverse()
+    //
+
+    // If we early-exit anywhere in this function, the drawableContentRect of this subtree should be considered empty.
+    drawableContentRectOfSubtree = gfx::Rect();
+
+    // The root layer cannot skip calcDrawProperties.
+    if (!isRootLayer(layer) && subtreeShouldBeSkipped(layer))
+        return;
+
+    // As this function proceeds, these are the properties for the current
+    // layer that actually get computed. To avoid unnecessary copies
+    // (particularly for matrices), we do computations directly on these values
+    // when possible.
+    DrawProperties<LayerType, RenderSurfaceType>& layerDrawProperties = layer->draw_properties();
+
+    gfx::Rect clipRectForSubtree;
+    bool subtreeShouldBeClipped = false;
+
+    // This value is cached on the stack so that we don't have to inverse-project
+    // the surface's clipRect redundantly for every layer. This value is the
+    // same as the surface's clipRect, except that instead of being described
+    // in the target surface space (i.e. the ancestor surface space), it is
+    // described in the current surface space.
+    gfx::Rect clipRectForSubtreeInDescendantSpace;
+
+    float accumulatedDrawOpacity = layer->opacity();
+    bool animatingOpacityToTarget = layer->OpacityIsAnimating();
+    bool animatingOpacityToScreen = animatingOpacityToTarget;
+    if (layer->parent()) {
+        accumulatedDrawOpacity *= layer->parent()->draw_opacity();
+        animatingOpacityToTarget |= layer->parent()->draw_opacity_is_animating();
+        animatingOpacityToScreen |= layer->parent()->screen_space_opacity_is_animating();
+    }
+
+    bool animatingTransformToTarget = layer->TransformIsAnimating();
+    bool animating_transform_to_screen = animatingTransformToTarget;
+    if (layer->parent()) {
+        animatingTransformToTarget |= layer->parent()->draw_transform_is_animating();
+        animating_transform_to_screen |= layer->parent()->screen_space_transform_is_animating();
+    }
+
+    gfx::Size bounds = layer->bounds();
+    gfx::PointF anchorPoint = layer->anchor_point();
+    gfx::PointF position = layer->position() - layer->scroll_delta();
+
+    gfx::Transform combinedTransform = parentMatrix;
+    if (!layer->transform().IsIdentity()) {
+        // LT = Tr[origin] * Tr[origin2anchor]
+        combinedTransform.Translate3d(position.x() + anchorPoint.x() * bounds.width(), position.y() + anchorPoint.y() * bounds.height(), layer->anchor_point_z());
+        // LT = Tr[origin] * Tr[origin2anchor] * M[layer]
+        combinedTransform.PreconcatTransform(layer->transform());
+        // LT = Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2origin]
+        combinedTransform.Translate3d(-anchorPoint.x() * bounds.width(), -anchorPoint.y() * bounds.height(), -layer->anchor_point_z());
     } else {
-      render_surface->SetClipRect(gfx::Rect());
-      clip_rect_for_subtree_in_descendant_space =
-          clip_rect_from_ancestor_in_descendant_space;
-    }
-
-    render_surface->SetNearestAncestorThatMovesPixels(
-        nearest_ancestor_that_moves_pixels);
-
-    // If the new render surface is drawn translucent or with a non-integral
-    // translation then the subtree that gets drawn on this render surface
-    // cannot use LCD text.
-    subtree_can_use_lcd_text = layer_can_use_lcd_text;
-
-    render_surface_layer_list->push_back(layer);
-  } else {
-    DCHECK(layer->parent());
-
-    // Note: layer_draw_properties.target_space_transform is computed above,
-    // before this if-else statement.
-    layer_draw_properties.target_space_transform_is_animating =
-        animating_transform_to_target;
-    layer_draw_properties.screen_space_transform_is_animating =
-        animating_transform_to_screen;
-    layer_draw_properties.opacity = accumulated_draw_opacity;
-    layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
-    layer_draw_properties.screen_space_opacity_is_animating =
-        animating_opacity_to_screen;
-    sublayer_matrix = combined_transform;
-
-    layer->ClearRenderSurface();
-
-    // Layers without render_surfaces directly inherit the ancestor's clip
-    // status.
-    subtree_should_be_clipped = ancestor_clips_subtree;
-    if (ancestor_clips_subtree)
-      clip_rect_for_subtree = clip_rect_from_ancestor;
-
-    // The surface's cached clipRect value propagates regardless of what
-    // clipping goes on between layers here.
-    clip_rect_for_subtree_in_descendant_space =
-        clip_rect_from_ancestor_in_descendant_space;
-
-    // Layers that are not their own render_target will render into the target
-    // of their nearest ancestor.
-    layer_draw_properties.render_target = layer->parent()->render_target();
-  }
-
-  if (adjust_text_aa)
-    layer_draw_properties.can_use_lcd_text = layer_can_use_lcd_text;
-
-  gfx::Rect rect_in_target_space = ToEnclosingRect(
-      MathUtil::MapClippedRect(layer->draw_transform(), content_rect));
-
-  if (LayerClipsSubtree(layer)) {
-    subtree_should_be_clipped = true;
-    if (ancestor_clips_subtree && !layer->render_surface()) {
-      clip_rect_for_subtree = clip_rect_from_ancestor;
-      clip_rect_for_subtree.Intersect(rect_in_target_space);
+        combinedTransform.Translate(position.x(), position.y());
+    }
+
+    // The layer's contentsSize is determined from the combinedTransform, which then informs the
+    // layer's drawTransform.
+    updateLayerContentsScale(layer, combinedTransform, deviceScaleFactor, pageScaleFactor, animating_transform_to_screen);
+
+    // If there is a transformation from the impl thread then it should be at
+    // the start of the combinedTransform, but we don't want it to affect the
+    // computation of contentsScale above.
+    // Note carefully: this is Concat, not Preconcat (implTransform * combinedTransform).
+    combinedTransform.ConcatTransform(layer->impl_transform());
+
+    if (!animatingTransformToTarget && layer->scrollable() && combinedTransform.IsScaleOrTranslation()) {
+        // Align the scrollable layer's position to screen space pixels to avoid blurriness.
+        // To avoid side-effects, do this only if the transform is simple.
+        roundTranslationComponents(&combinedTransform);
+    }
+
+    if (layer->fixed_to_container_layer()) {
+        // Special case: this layer is a composited fixed-position layer; we need to
+        // explicitly compensate for all ancestors' nonzero scrollDeltas to keep this layer
+        // fixed correctly.
+        // Note carefully: this is Concat, not Preconcat (currentScrollCompensation * combinedTransform).
+        combinedTransform.ConcatTransform(currentScrollCompensationMatrix);
+    }
+
+    // The drawTransform that gets computed below is effectively the layer's drawTransform, unless
+    // the layer itself creates a renderSurface. In that case, the renderSurface re-parents the transforms.
+    layerDrawProperties.target_space_transform = combinedTransform;
+    // M[draw] = M[parent] * LT * S[layer2content]
+    layerDrawProperties.target_space_transform.Scale(1.0 / layer->contents_scale_x(), 1.0 / layer->contents_scale_y());
+
+    // layerScreenSpaceTransform represents the transform between root layer's "screen space" and local content space.
+    layerDrawProperties.screen_space_transform = fullHierarchyMatrix;
+    if (!layer->preserves_3d())
+        layerDrawProperties.screen_space_transform.FlattenTo2d();
+    layerDrawProperties.screen_space_transform.PreconcatTransform(layerDrawProperties.target_space_transform);
+
+    // Adjusting text AA method during animation may cause repaints, which in-turn causes jank.
+    bool adjustTextAA = !animatingOpacityToScreen && !animating_transform_to_screen;
+    // To avoid color fringing, LCD text should only be used on opaque layers with just integral translation.
+    bool layerCanUseLCDText = subtreeCanUseLCDText &&
+                              (accumulatedDrawOpacity == 1.0) &&
+                              layerDrawProperties.target_space_transform.IsIdentityOrIntegerTranslation();
+
+    gfx::RectF contentRect(gfx::PointF(), layer->content_bounds());
+
+    // fullHierarchyMatrix is the matrix that transforms objects between screen space (except projection matrix) and the most recent RenderSurfaceImpl's space.
+    // nextHierarchyMatrix will only change if this layer uses a new RenderSurfaceImpl, otherwise remains the same.
+    gfx::Transform nextHierarchyMatrix = fullHierarchyMatrix;
+    gfx::Transform sublayerMatrix;
+
+    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
+
+    if (subtreeShouldRenderToSeparateSurface(layer, combinedTransform.IsScaleOrTranslation())) {
+        // Check back-face visibility before continuing with this surface and its subtree
+        if (!layer->double_sided() && transformToParentIsKnown(layer) && isSurfaceBackFaceVisible(layer, combinedTransform))
+            return;
+
+        if (!layer->render_surface())
+            layer->CreateRenderSurface();
+
+        RenderSurfaceType* renderSurface = layer->render_surface();
+        renderSurface->ClearLayerLists();
+
+        // The owning layer's draw transform has a scale from content to layer
+        // space which we do not want; so here we use the combinedTransform
+        // instead of the drawTransform. However, we do need to add a different
+        // scale factor that accounts for the surface's pixel dimensions.
+        combinedTransform.Scale(1 / renderSurfaceSublayerScale.x(), 1 / renderSurfaceSublayerScale.y());
+        renderSurface->SetDrawTransform(combinedTransform);
+
+        // The owning layer's transform was re-parented by the surface, so the layer's new drawTransform
+        // only needs to scale the layer to surface space.
+        layerDrawProperties.target_space_transform.MakeIdentity();
+        layerDrawProperties.target_space_transform.Scale(renderSurfaceSublayerScale.x() / layer->contents_scale_x(), renderSurfaceSublayerScale.y() / layer->contents_scale_y());
+
+        // Inside the surface's subtree, we scale everything to the owning layer's scale.
+        // The sublayer matrix transforms layer rects into target
+        // surface content space.
+        DCHECK(sublayerMatrix.IsIdentity());
+        sublayerMatrix.Scale(renderSurfaceSublayerScale.x(), renderSurfaceSublayerScale.y());
+
+        // The opacity value is moved from the layer to its surface, so that the entire subtree properly inherits opacity.
+        renderSurface->SetDrawOpacity(accumulatedDrawOpacity);
+        renderSurface->SetDrawOpacityIsAnimating(animatingOpacityToTarget);
+        animatingOpacityToTarget = false;
+        layerDrawProperties.opacity = 1;
+        layerDrawProperties.opacity_is_animating = animatingOpacityToTarget;
+        layerDrawProperties.screen_space_opacity_is_animating = animatingOpacityToScreen;
+
+        renderSurface->SetTargetSurfaceTransformsAreAnimating(animatingTransformToTarget);
+        renderSurface->SetScreenSpaceTransformsAreAnimating(animating_transform_to_screen);
+        animatingTransformToTarget = false;
+        layerDrawProperties.target_space_transform_is_animating = animatingTransformToTarget;
+        layerDrawProperties.screen_space_transform_is_animating = animating_transform_to_screen;
+
+        // Update the aggregate hierarchy matrix to include the transform of the
+        // newly created RenderSurfaceImpl.
+        nextHierarchyMatrix.PreconcatTransform(renderSurface->draw_transform());
+
+        // The new renderSurface here will correctly clip the entire subtree. So, we do
+        // not need to continue propagating the clipping state further down the tree. This
+        // way, we can avoid transforming clipRects from ancestor target surface space to
+        // current target surface space that could cause more w < 0 headaches.
+        subtreeShouldBeClipped = false;
+
+        if (layer->mask_layer()) {
+            DrawProperties<LayerType, RenderSurfaceType>& maskLayerDrawProperties = layer->mask_layer()->draw_properties();
+            maskLayerDrawProperties.render_target = layer;
+            maskLayerDrawProperties.visible_content_rect = gfx::Rect(gfx::Point(), layer->content_bounds());
+        }
+
+        if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
+            DrawProperties<LayerType, RenderSurfaceType>& replicaMaskDrawProperties = layer->replica_layer()->mask_layer()->draw_properties();
+            replicaMaskDrawProperties.render_target = layer;
+            replicaMaskDrawProperties.visible_content_rect = gfx::Rect(gfx::Point(), layer->content_bounds());
+        }
+
+        // FIXME:  make this smarter for the SkImageFilter case (check for
+        //         pixel-moving filters)
+        if (layer->filters().hasFilterThatMovesPixels() || layer->filter())
+            nearestAncestorThatMovesPixels = renderSurface;
+
+        // The render surface clipRect is expressed in the space where this surface draws, i.e. the same space as clipRectFromAncestor.
+        renderSurface->SetIsClipped(ancestorClipsSubtree);
+        if (ancestorClipsSubtree) {
+            renderSurface->SetClipRect(clipRectFromAncestor);
+
+            gfx::Transform inverseSurfaceDrawTransform(gfx::Transform::kSkipInitialization);
+            if (!renderSurface->draw_transform().GetInverse(&inverseSurfaceDrawTransform)) {
+                // TODO(shawnsingh): Either we need to handle uninvertible transforms
+                // here, or DCHECK that the transform is invertible.
+            }
+            clipRectForSubtreeInDescendantSpace = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(inverseSurfaceDrawTransform, renderSurface->clip_rect()));
+        } else {
+            renderSurface->SetClipRect(gfx::Rect());
+            clipRectForSubtreeInDescendantSpace = clipRectFromAncestorInDescendantSpace;
+        }
+
+        renderSurface->SetNearestAncestorThatMovesPixels(nearestAncestorThatMovesPixels);
+
+        // If the new render surface is drawn translucent or with a non-integral translation
+        // then the subtree that gets drawn on this render surface cannot use LCD text.
+        subtreeCanUseLCDText = layerCanUseLCDText;
+
+        renderSurfaceLayerList.push_back(layer);
     } else {
-      clip_rect_for_subtree = rect_in_target_space;
-    }
-  }
-
-  // Flatten to 2D if the layer doesn't preserve 3D.
-  if (!layer->preserves_3d())
-    sublayer_matrix.FlattenTo2d();
-
-  // Apply the sublayer transform at the anchor point of the layer.
-  if (!layer->sublayer_transform().IsIdentity()) {
-    sublayer_matrix.Translate(layer->anchor_point().x() * bounds.width(),
-                              layer->anchor_point().y() * bounds.height());
-    sublayer_matrix.PreconcatTransform(layer->sublayer_transform());
-    sublayer_matrix.Translate(-layer->anchor_point().x() * bounds.width(),
-                              -layer->anchor_point().y() * bounds.height());
-  }
-
-  LayerList& descendants =
-      (layer->render_surface() ? layer->render_surface()->layer_list()
-                               : *layer_list);
-
-  // Any layers that are appended after this point are in the layer's subtree
-  // and should be included in the sorting process.
-  size_t sorting_start_index = descendants.size();
-
-  if (!LayerShouldBeSkipped(layer))
-    descendants.push_back(layer);
-
-  gfx::Transform next_scroll_compensation_matrix =
-      ComputeScrollCompensationMatrixForChildren(
-          layer, parent_matrix, current_scroll_compensation_matrix);
-
-  gfx::Rect accumulated_drawable_content_rect_of_children;
-  for (size_t i = 0; i < layer->children().size(); ++i) {
-    LayerType* child =
-        LayerTreeHostCommon::get_child_as_raw_ptr(layer->children(), i);
-    gfx::Rect drawable_content_rect_of_child_subtree;
-    CalculateDrawPropertiesInternal<LayerType, LayerList, RenderSurfaceType>(
-        child,
-        sublayer_matrix,
-        next_hierarchy_matrix,
-        next_scroll_compensation_matrix,
-        clip_rect_for_subtree,
-        clip_rect_for_subtree_in_descendant_space,
-        subtree_should_be_clipped,
-        nearest_ancestor_that_moves_pixels,
-        render_surface_layer_list,
-        &descendants,
-        layer_sorter,
-        max_texture_size,
-        device_scale_factor,
-        page_scale_factor,
-        subtree_can_use_lcd_text,
-        &drawable_content_rect_of_child_subtree,
-        update_tile_priorities);
-    if (!drawable_content_rect_of_child_subtree.IsEmpty()) {
-      accumulated_drawable_content_rect_of_children.Union(
-          drawable_content_rect_of_child_subtree);
-      if (child->render_surface())
-        descendants.push_back(child);
-    }
-  }
-
-  if (layer->render_surface() && !IsRootLayer(layer) &&
-      layer->render_surface()->layer_list().empty()) {
-    RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
-    return;
-  }
-
-  // Compute the total drawableContentRect for this subtree (the rect is in
-  // targetSurface space).
-  gfx::Rect local_drawable_content_rect_of_subtree =
-      accumulated_drawable_content_rect_of_children;
-  if (layer->DrawsContent())
-    local_drawable_content_rect_of_subtree.Union(rect_in_target_space);
-  if (subtree_should_be_clipped)
-    local_drawable_content_rect_of_subtree.Intersect(clip_rect_for_subtree);
-
-  // Compute the layer's drawable content rect (the rect is in targetSurface
-  // space).
-  layer_draw_properties.drawable_content_rect = rect_in_target_space;
-  if (subtree_should_be_clipped) {
-    layer_draw_properties.drawable_content_rect.
-        Intersect(clip_rect_for_subtree);
-  }
-
-  // Tell the layer the rect that is clipped by. In theory we could use a
-  // tighter clipRect here (drawableContentRect), but that actually does not
-  // reduce how much would be drawn, and instead it would create unnecessary
-  // changes to scissor state affecting GPU performance.
-  layer_draw_properties.is_clipped = subtree_should_be_clipped;
-  if (subtree_should_be_clipped) {
-    layer_draw_properties.clip_rect = clip_rect_for_subtree;
-  } else {
-    // Initialize the clipRect to a safe value that will not clip the
-    // layer, just in case clipping is still accidentally used.
-    layer_draw_properties.clip_rect = rect_in_target_space;
-  }
-
-  // Compute the layer's visible content rect (the rect is in content space)
-  layer_draw_properties.visible_content_rect = CalculateVisibleContentRect(
-      layer, clip_rect_for_subtree_in_descendant_space, rect_in_target_space);
-
-  // Compute the remaining properties for the render surface, if the layer has
-  // one.
-  if (IsRootLayer(layer)) {
-    // The root layer's surface's content_rect is always the entire viewport.
-    DCHECK(layer->render_surface());
-    layer->render_surface()->SetContentRect(clip_rect_from_ancestor);
-  } else if (layer->render_surface() && !IsRootLayer(layer)) {
-    RenderSurfaceType* render_surface = layer->render_surface();
-    gfx::Rect clipped_content_rect = local_drawable_content_rect_of_subtree;
-
-    // Don't clip if the layer is reflected as the reflection shouldn't be
-    // clipped. If the layer is animating, then the surface's transform to
-    // its target is not known on the main thread, and we should not use it
-    // to clip.
-    if (!layer->replica_layer() && TransformToParentIsKnown(layer)) {
-      // Note, it is correct to use ancestor_clips_subtree here, because we are
-      // looking at this layer's render_surface, not the layer itself.
-      if (ancestor_clips_subtree && !clipped_content_rect.IsEmpty()) {
-        gfx::Rect surface_clip_rect = LayerTreeHostCommon::CalculateVisibleRect(
-            render_surface->clip_rect(),
-            clipped_content_rect,
-            render_surface->draw_transform());
-        clipped_content_rect.Intersect(surface_clip_rect);
-      }
-    }
-
-    // The RenderSurfaceImpl backing texture cannot exceed the maximum supported
-    // texture size.
-    clipped_content_rect.set_width(
-        std::min(clipped_content_rect.width(), max_texture_size));
-    clipped_content_rect.set_height(
-        std::min(clipped_content_rect.height(), max_texture_size));
-
-    if (clipped_content_rect.IsEmpty()) {
-      render_surface->ClearLayerLists();
-      RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
-      return;
-    }
-
-    render_surface->SetContentRect(clipped_content_rect);
-
-    // The owning layer's screen_space_transform has a scale from content to
-    // layer space which we need to undo and replace with a scale from the
-    // surface's subtree into layer space.
-    gfx::Transform screen_space_transform = layer->screen_space_transform();
-    screen_space_transform.Scale(
-        layer->contents_scale_x() / render_surface_sublayer_scale.x(),
-        layer->contents_scale_y() / render_surface_sublayer_scale.y());
-    render_surface->SetScreenSpaceTransform(screen_space_transform);
-
-    if (layer->replica_layer()) {
-      gfx::Transform surface_origin_to_replica_origin_transform;
-      surface_origin_to_replica_origin_transform.Scale(
-          render_surface_sublayer_scale.x(), render_surface_sublayer_scale.y());
-      surface_origin_to_replica_origin_transform.Translate(
-          layer->replica_layer()->position().x() +
-          layer->replica_layer()->anchor_point().x() * bounds.width(),
-          layer->replica_layer()->position().y() +
-          layer->replica_layer()->anchor_point().y() * bounds.height());
-      surface_origin_to_replica_origin_transform.PreconcatTransform(
-          layer->replica_layer()->transform());
-      surface_origin_to_replica_origin_transform.Translate(
-          -layer->replica_layer()->anchor_point().x() * bounds.width(),
-          -layer->replica_layer()->anchor_point().y() * bounds.height());
-      surface_origin_to_replica_origin_transform.Scale(
-          1.0 / render_surface_sublayer_scale.x(),
-          1.0 / render_surface_sublayer_scale.y());
-
-      // Compute the replica's "originTransform" that maps from the replica's
-      // origin space to the target surface origin space.
-      gfx::Transform replica_origin_transform =
-          layer->render_surface()->draw_transform() *
-          surface_origin_to_replica_origin_transform;
-      render_surface->SetReplicaDrawTransform(replica_origin_transform);
-
-      // Compute the replica's "screen_space_transform" that maps from the
-      // replica's origin space to the screen's origin space.
-      gfx::Transform replica_screen_space_transform =
-          layer->render_surface()->screen_space_transform() *
-          surface_origin_to_replica_origin_transform;
-      render_surface->SetReplicaScreenSpaceTransform(
-          replica_screen_space_transform);
-    }
-  }
-
-  if (update_tile_priorities)
-    UpdateTilePrioritiesForLayer(layer);
-
-  // If neither this layer nor any of its children were added, early out.
-  if (sorting_start_index == descendants.size())
-    return;
-
-  // If preserves-3d then sort all the descendants in 3D so that they can be
-  // drawn from back to front. If the preserves-3d property is also set on the
-  // parent then skip the sorting as the parent will sort all the descendants
-  // anyway.
-  if (layer_sorter && descendants.size() && layer->preserves_3d() &&
-      (!layer->parent() || !layer->parent()->preserves_3d())) {
-    SortLayers(descendants.begin() + sorting_start_index,
-               descendants.end(),
-               layer_sorter);
-  }
-
-  if (layer->render_surface()) {
-    *drawable_content_rect_of_subtree =
-        gfx::ToEnclosingRect(layer->render_surface()->DrawableContentRect());
-  } else {
-    *drawable_content_rect_of_subtree = local_drawable_content_rect_of_subtree;
-  }
-
-  if (layer->HasContributingDelegatedRenderPasses()) {
-    layer->render_target()->render_surface()->
-        AddContributingDelegatedRenderPassLayer(layer);
-  }
-}
-
-void LayerTreeHostCommon::CalculateDrawProperties(
-    Layer* root_layer,
-    gfx::Size device_viewport_size,
-    float device_scale_factor,
-    float page_scale_factor,
-    int max_texture_size,
-    bool can_use_lcd_text,
-    std::vector<scoped_refptr<Layer> >* render_surface_layer_list) {
-  gfx::Rect total_drawable_content_rect;
-  gfx::Transform identity_matrix;
-  gfx::Transform device_scale_transform;
-  device_scale_transform.Scale(device_scale_factor, device_scale_factor);
-  std::vector<scoped_refptr<Layer> > dummy_layer_list;
-
-  // The root layer's render_surface should receive the deviceViewport as the
-  // initial clipRect.
-  bool subtree_should_be_clipped = true;
-  gfx::Rect device_viewport_rect(gfx::Point(), device_viewport_size);
-  bool update_tile_priorities = false;
-
-  // This function should have received a root layer.
-  DCHECK(IsRootLayer(root_layer));
-
-  PreCalculateMetaInformation<Layer>(root_layer);
-  CalculateDrawPropertiesInternal<Layer,
-                                  std::vector<scoped_refptr<Layer> >,
-                                  RenderSurface>(root_layer,
-                                                 device_scale_transform,
-                                                 identity_matrix,
-                                                 identity_matrix,
-                                                 device_viewport_rect,
-                                                 device_viewport_rect,
-                                                 subtree_should_be_clipped,
-                                                 NULL,
-                                                 render_surface_layer_list,
-                                                 &dummy_layer_list,
-                                                 NULL,
-                                                 max_texture_size,
-                                                 device_scale_factor,
-                                                 page_scale_factor,
-                                                 can_use_lcd_text,
-                                                 &total_drawable_content_rect,
-                                                 update_tile_priorities);
-
-  // The dummy layer list should not have been used.
-  DCHECK_EQ(dummy_layer_list.size(), 0);
-  // A root layer render_surface should always exist after
-  // calculateDrawProperties.
-  DCHECK(root_layer->render_surface());
-}
-
-void LayerTreeHostCommon::CalculateDrawProperties(
-    LayerImpl* root_layer,
-    gfx::Size device_viewport_size,
-    float device_scale_factor,
-    float page_scale_factor,
-    int max_texture_size,
-    bool can_use_lcd_text,
-    std::vector<LayerImpl*>* render_surface_layer_list,
-    bool update_tile_priorities) {
-  gfx::Rect total_drawable_content_rect;
-  gfx::Transform identity_matrix;
-  gfx::Transform device_scale_transform;
-  device_scale_transform.Scale(device_scale_factor, device_scale_factor);
-  std::vector<LayerImpl*> dummy_layer_list;
-  LayerSorter layer_sorter;
-
-  // The root layer's render_surface should receive the deviceViewport as the
-  // initial clipRect.
-  bool subtree_should_be_clipped = true;
-  gfx::Rect device_viewport_rect(gfx::Point(), device_viewport_size);
-
-  // This function should have received a root layer.
-  DCHECK(IsRootLayer(root_layer));
-
-  PreCalculateMetaInformation<LayerImpl>(root_layer);
-  CalculateDrawPropertiesInternal<LayerImpl,
-                                  std::vector<LayerImpl*>,
-                                  RenderSurfaceImpl>(
-      root_layer,
-      device_scale_transform,
-      identity_matrix,
-      identity_matrix,
-      device_viewport_rect,
-      device_viewport_rect,
-      subtree_should_be_clipped,
-      NULL,
-      render_surface_layer_list,
-      &dummy_layer_list,
-      &layer_sorter,
-      max_texture_size,
-      device_scale_factor,
-      page_scale_factor,
-      can_use_lcd_text,
-      &total_drawable_content_rect,
-      update_tile_priorities);
-
-  // The dummy layer list should not have been used.
-  DCHECK_EQ(dummy_layer_list.size(), 0);
-  // A root layer render_surface should always exist after
-  // calculateDrawProperties.
-  DCHECK(root_layer->render_surface());
-}
-
-static bool PointHitsRect(
-    gfx::PointF screen_space_point,
-    const gfx::Transform& local_space_to_screen_space_transform,
-    gfx::RectF local_space_rect) {
-  // If the transform is not invertible, then assume that this point doesn't hit
-  // this rect.
-  gfx::Transform inverse_local_space_to_screen_space(
-      gfx::Transform::kSkipInitialization);
-  if (!local_space_to_screen_space_transform.GetInverse(
-          &inverse_local_space_to_screen_space))
+        DCHECK(layer->parent());
+
+        // Note: layerDrawProperties.target_space_transform is computed above,
+        // before this if-else statement.
+        layerDrawProperties.target_space_transform_is_animating = animatingTransformToTarget;
+        layerDrawProperties.screen_space_transform_is_animating = animating_transform_to_screen;
+        layerDrawProperties.opacity = accumulatedDrawOpacity;
+        layerDrawProperties.opacity_is_animating = animatingOpacityToTarget;
+        layerDrawProperties.screen_space_opacity_is_animating = animatingOpacityToScreen;
+        sublayerMatrix = combinedTransform;
+
+        layer->ClearRenderSurface();
+
+        // Layers without renderSurfaces directly inherit the ancestor's clip status.
+        subtreeShouldBeClipped = ancestorClipsSubtree;
+        if (ancestorClipsSubtree)
+            clipRectForSubtree = clipRectFromAncestor;
+
+        // The surface's cached clipRect value propagates regardless of what clipping goes on between layers here.
+        clipRectForSubtreeInDescendantSpace = clipRectFromAncestorInDescendantSpace;
+
+        // Layers that are not their own renderTarget will render into the target of their nearest ancestor.
+        layerDrawProperties.render_target = layer->parent()->render_target();
+    }
+
+    if (adjustTextAA)
+        layerDrawProperties.can_use_lcd_text = layerCanUseLCDText;
+
+    gfx::Rect rectInTargetSpace = ToEnclosingRect(MathUtil::MapClippedRect(layer->draw_transform(), contentRect));
+
+    if (layerClipsSubtree(layer)) {
+        subtreeShouldBeClipped = true;
+        if (ancestorClipsSubtree && !layer->render_surface()) {
+            clipRectForSubtree = clipRectFromAncestor;
+            clipRectForSubtree.Intersect(rectInTargetSpace);
+        } else
+            clipRectForSubtree = rectInTargetSpace;
+    }
+
+    // Flatten to 2D if the layer doesn't preserve 3D.
+    if (!layer->preserves_3d())
+        sublayerMatrix.FlattenTo2d();
+
+    // Apply the sublayer transform at the anchor point of the layer.
+    if (!layer->sublayer_transform().IsIdentity()) {
+        sublayerMatrix.Translate(layer->anchor_point().x() * bounds.width(), layer->anchor_point().y() * bounds.height());
+        sublayerMatrix.PreconcatTransform(layer->sublayer_transform());
+        sublayerMatrix.Translate(-layer->anchor_point().x() * bounds.width(), -layer->anchor_point().y() * bounds.height());
+    }
+
+    LayerList& descendants = (layer->render_surface() ? layer->render_surface()->layer_list() : layerList);
+
+    // Any layers that are appended after this point are in the layer's subtree and should be included in the sorting process.
+    unsigned sortingStartIndex = descendants.size();
+
+    if (!layerShouldBeSkipped(layer))
+        descendants.push_back(layer);
+
+    gfx::Transform nextScrollCompensationMatrix = computeScrollCompensationMatrixForChildren(layer, parentMatrix, currentScrollCompensationMatrix);;
+
+    gfx::Rect accumulatedDrawableContentRectOfChildren;
+    for (size_t i = 0; i < layer->children().size(); ++i) {
+        LayerType* child = LayerTreeHostCommon::getChildAsRawPtr(layer->children(), i);
+        gfx::Rect drawableContentRectOfChildSubtree;
+        calculateDrawPropertiesInternal<LayerType, LayerList, RenderSurfaceType>(child, sublayerMatrix, nextHierarchyMatrix, nextScrollCompensationMatrix,
+                                                                                 clipRectForSubtree, clipRectForSubtreeInDescendantSpace, subtreeShouldBeClipped, nearestAncestorThatMovesPixels,
+                                                                                 renderSurfaceLayerList, descendants, layerSorter, maxTextureSize, deviceScaleFactor, pageScaleFactor,
+                                                                                 subtreeCanUseLCDText, drawableContentRectOfChildSubtree, updateTilePriorities);
+        if (!drawableContentRectOfChildSubtree.IsEmpty()) {
+            accumulatedDrawableContentRectOfChildren.Union(drawableContentRectOfChildSubtree);
+            if (child->render_surface())
+                descendants.push_back(child);
+        }
+    }
+
+    if (layer->render_surface() && !isRootLayer(layer) && !layer->render_surface()->layer_list().size()) {
+        removeSurfaceForEarlyExit(layer, renderSurfaceLayerList);
+        return;
+    }
+    
+    // Compute the total drawableContentRect for this subtree (the rect is in targetSurface space)
+    gfx::Rect localDrawableContentRectOfSubtree = accumulatedDrawableContentRectOfChildren;
+    if (layer->DrawsContent())
+        localDrawableContentRectOfSubtree.Union(rectInTargetSpace);
+    if (subtreeShouldBeClipped)
+        localDrawableContentRectOfSubtree.Intersect(clipRectForSubtree);
+
+    // Compute the layer's drawable content rect (the rect is in targetSurface space)
+    layerDrawProperties.drawable_content_rect = rectInTargetSpace;
+    if (subtreeShouldBeClipped)
+        layerDrawProperties.drawable_content_rect.Intersect(clipRectForSubtree);
+
+    // Tell the layer the rect that is clipped by. In theory we could use a
+    // tighter clipRect here (drawableContentRect), but that actually does not
+    // reduce how much would be drawn, and instead it would create unnecessary
+    // changes to scissor state affecting GPU performance.
+    layerDrawProperties.is_clipped = subtreeShouldBeClipped;
+    if (subtreeShouldBeClipped)
+        layerDrawProperties.clip_rect = clipRectForSubtree;
+    else {
+        // Initialize the clipRect to a safe value that will not clip the
+        // layer, just in case clipping is still accidentally used.
+        layerDrawProperties.clip_rect = rectInTargetSpace;
+    }
+
+    // Compute the layer's visible content rect (the rect is in content space)
+    layerDrawProperties.visible_content_rect = calculateVisibleContentRect(layer, clipRectForSubtreeInDescendantSpace, rectInTargetSpace);
+
+    // Compute the remaining properties for the render surface, if the layer has one.
+    if (isRootLayer(layer)) {
+        // The root layer's surface's contentRect is always the entire viewport.
+        DCHECK(layer->render_surface());
+        layer->render_surface()->SetContentRect(clipRectFromAncestor);
+    } else if (layer->render_surface() && !isRootLayer(layer)) {
+        RenderSurfaceType* renderSurface = layer->render_surface();
+        gfx::Rect clippedContentRect = localDrawableContentRectOfSubtree;
+
+        // Don't clip if the layer is reflected as the reflection shouldn't be
+        // clipped. If the layer is animating, then the surface's transform to
+        // its target is not known on the main thread, and we should not use it
+        // to clip.
+        if (!layer->replica_layer() && transformToParentIsKnown(layer)) {
+            // Note, it is correct to use ancestorClipsSubtree here, because we are looking at this layer's renderSurface, not the layer itself.
+            if (ancestorClipsSubtree && !clippedContentRect.IsEmpty()) {
+                gfx::Rect surfaceClipRect = LayerTreeHostCommon::calculateVisibleRect(renderSurface->clip_rect(), clippedContentRect, renderSurface->draw_transform());
+                clippedContentRect.Intersect(surfaceClipRect);
+            }
+        }
+
+        // The RenderSurfaceImpl backing texture cannot exceed the maximum supported
+        // texture size.
+        clippedContentRect.set_width(std::min(clippedContentRect.width(), maxTextureSize));
+        clippedContentRect.set_height(std::min(clippedContentRect.height(), maxTextureSize));
+
+        if (clippedContentRect.IsEmpty()) {
+            renderSurface->ClearLayerLists();
+            removeSurfaceForEarlyExit(layer, renderSurfaceLayerList);
+            return;
+        }
+        
+        renderSurface->SetContentRect(clippedContentRect);
+
+        // The owning layer's screenSpaceTransform has a scale from content to layer space which we need to undo and
+        // replace with a scale from the surface's subtree into layer space.
+        gfx::Transform screenSpaceTransform = layer->screen_space_transform();
+        screenSpaceTransform.Scale(layer->contents_scale_x() / renderSurfaceSublayerScale.x(), layer->contents_scale_y() / renderSurfaceSublayerScale.y());
+        renderSurface->SetScreenSpaceTransform(screenSpaceTransform);
+
+        if (layer->replica_layer()) {
+            gfx::Transform surfaceOriginToReplicaOriginTransform;
+            surfaceOriginToReplicaOriginTransform.Scale(renderSurfaceSublayerScale.x(), renderSurfaceSublayerScale.y());
+            surfaceOriginToReplicaOriginTransform.Translate(layer->replica_layer()->position().x() + layer->replica_layer()->anchor_point().x() * bounds.width(),
+                                                            layer->replica_layer()->position().y() + layer->replica_layer()->anchor_point().y() * bounds.height());
+            surfaceOriginToReplicaOriginTransform.PreconcatTransform(layer->replica_layer()->transform());
+            surfaceOriginToReplicaOriginTransform.Translate(-layer->replica_layer()->anchor_point().x() * bounds.width(), -layer->replica_layer()->anchor_point().y() * bounds.height());
+            surfaceOriginToReplicaOriginTransform.Scale(1 / renderSurfaceSublayerScale.x(), 1 / renderSurfaceSublayerScale.y());
+
+            // Compute the replica's "originTransform" that maps from the replica's origin space to the target surface origin space.
+            gfx::Transform replicaOriginTransform = layer->render_surface()->draw_transform() * surfaceOriginToReplicaOriginTransform;
+            renderSurface->SetReplicaDrawTransform(replicaOriginTransform);
+
+            // Compute the replica's "screenSpaceTransform" that maps from the replica's origin space to the screen's origin space.
+            gfx::Transform replicaScreenSpaceTransform = layer->render_surface()->screen_space_transform() * surfaceOriginToReplicaOriginTransform;
+            renderSurface->SetReplicaScreenSpaceTransform(replicaScreenSpaceTransform);
+        }
+    }
+
+    if (updateTilePriorities)
+        updateTilePrioritiesForLayer(layer);
+
+    // If neither this layer nor any of its children were added, early out.
+    if (sortingStartIndex == descendants.size())
+        return;
+
+    // If preserves-3d then sort all the descendants in 3D so that they can be
+    // drawn from back to front. If the preserves-3d property is also set on the parent then
+    // skip the sorting as the parent will sort all the descendants anyway.
+    if (layerSorter && descendants.size() && layer->preserves_3d() && (!layer->parent() || !layer->parent()->preserves_3d()))
+        sortLayers(descendants.begin() + sortingStartIndex, descendants.end(), layerSorter);
+
+    if (layer->render_surface())
+        drawableContentRectOfSubtree = gfx::ToEnclosingRect(layer->render_surface()->DrawableContentRect());
+    else
+        drawableContentRectOfSubtree = localDrawableContentRectOfSubtree;
+
+    if (layer->HasContributingDelegatedRenderPasses())
+        layer->render_target()->render_surface()->AddContributingDelegatedRenderPassLayer(layer);
+}
+
+void LayerTreeHostCommon::calculateDrawProperties(Layer* rootLayer, const gfx::Size& deviceViewportSize, float deviceScaleFactor, float pageScaleFactor, int maxTextureSize, bool canUseLCDText, std::vector<scoped_refptr<Layer> >& renderSurfaceLayerList)
+{
+    gfx::Rect totalDrawableContentRect;
+    gfx::Transform identityMatrix;
+    gfx::Transform deviceScaleTransform;
+    deviceScaleTransform.Scale(deviceScaleFactor, deviceScaleFactor);
+    std::vector<scoped_refptr<Layer> > dummyLayerList;
+
+    // The root layer's renderSurface should receive the deviceViewport as the initial clipRect.
+    bool subtreeShouldBeClipped = true;
+    gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
+    bool updateTilePriorities = false;
+
+    // This function should have received a root layer.
+    DCHECK(isRootLayer(rootLayer));
+
+    preCalculateMetaInformation<Layer>(rootLayer);
+    calculateDrawPropertiesInternal<Layer, std::vector<scoped_refptr<Layer> >, RenderSurface>(
+        rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
+        deviceViewportRect, deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
+        dummyLayerList, 0, maxTextureSize,
+        deviceScaleFactor, pageScaleFactor, canUseLCDText, totalDrawableContentRect,
+        updateTilePriorities);
+
+    // The dummy layer list should not have been used.
+    DCHECK(dummyLayerList.size() == 0);
+    // A root layer renderSurface should always exist after calculateDrawProperties.
+    DCHECK(rootLayer->render_surface());
+}
+
+void LayerTreeHostCommon::calculateDrawProperties(LayerImpl* rootLayer, const gfx::Size& deviceViewportSize, float deviceScaleFactor, float pageScaleFactor, int maxTextureSize, bool canUseLCDText, std::vector<LayerImpl*>& renderSurfaceLayerList, bool updateTilePriorities)
+{
+    gfx::Rect totalDrawableContentRect;
+    gfx::Transform identityMatrix;
+    gfx::Transform deviceScaleTransform;
+    deviceScaleTransform.Scale(deviceScaleFactor, deviceScaleFactor);
+    std::vector<LayerImpl*> dummyLayerList;
+    LayerSorter layerSorter;
+    
+    // The root layer's renderSurface should receive the deviceViewport as the initial clipRect.
+    bool subtreeShouldBeClipped = true;
+    gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
+
+    // This function should have received a root layer.
+    DCHECK(isRootLayer(rootLayer));
+
+    preCalculateMetaInformation<LayerImpl>(rootLayer);
+    calculateDrawPropertiesInternal<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl>(
+        rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
+        deviceViewportRect, deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
+        dummyLayerList, &layerSorter, maxTextureSize,
+        deviceScaleFactor, pageScaleFactor, canUseLCDText, totalDrawableContentRect,
+        updateTilePriorities);
+
+    // The dummy layer list should not have been used.
+    DCHECK(dummyLayerList.size() == 0);
+    // A root layer renderSurface should always exist after calculateDrawProperties.
+    DCHECK(rootLayer->render_surface());
+}
+
+static bool pointHitsRect(const gfx::PointF& screenSpacePoint, const gfx::Transform& localSpaceToScreenSpaceTransform, gfx::RectF localSpaceRect)
+{
+    // If the transform is not invertible, then assume that this point doesn't hit this rect.
+    gfx::Transform inverseLocalSpaceToScreenSpace(gfx::Transform::kSkipInitialization);
+    if (!localSpaceToScreenSpaceTransform.GetInverse(&inverseLocalSpaceToScreenSpace))
+        return false;
+
+    // Transform the hit test point from screen space to the local space of the given rect.
+    bool clipped = false;
+    gfx::PointF hitTestPointInLocalSpace = MathUtil::ProjectPoint(inverseLocalSpaceToScreenSpace, screenSpacePoint, &clipped);
+
+    // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this rect.
+    if (clipped)
+        return false;
+
+    return localSpaceRect.Contains(hitTestPointInLocalSpace);
+}
+
+static bool pointHitsRegion(gfx::PointF screenSpacePoint, const gfx::Transform& screenSpaceTransform, const Region& layerSpaceRegion, float layerContentScaleX, float layerContentScaleY)
+{
+    // If the transform is not invertible, then assume that this point doesn't hit this region.
+    gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
+    if (!screenSpaceTransform.GetInverse(&inverseScreenSpaceTransform))
+        return false;
+
+    // Transform the hit test point from screen space to the local space of the given region.
+    bool clipped = false;
+    gfx::PointF hitTestPointInContentSpace = MathUtil::ProjectPoint(inverseScreenSpaceTransform, screenSpacePoint, &clipped);
+    gfx::PointF hitTestPointInLayerSpace = gfx::ScalePoint(hitTestPointInContentSpace, 1 / layerContentScaleX, 1 / layerContentScaleY);
+
+    // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this region.
+    if (clipped)
+        return false;
+
+    return layerSpaceRegion.Contains(gfx::ToRoundedPoint(hitTestPointInLayerSpace));
+}
+
+static bool pointIsClippedBySurfaceOrClipRect(const gfx::PointF& screenSpacePoint, LayerImpl* layer)
+{
+    LayerImpl* current_layer = layer;
+
+    // Walk up the layer tree and hit-test any renderSurfaces and any layer clipRects that are active.
+    while (current_layer) {
+        if (current_layer->render_surface() && !pointHitsRect(screenSpacePoint, current_layer->render_surface()->screen_space_transform(), current_layer->render_surface()->content_rect()))
+            return true;
+
+        // Note that drawableContentRects are actually in targetSurface space, so the transform we
+        // have to provide is the target surface's screenSpaceTransform.
+        LayerImpl* renderTarget = current_layer->render_target();
+        if (layerClipsSubtree(current_layer) && !pointHitsRect(screenSpacePoint, renderTarget->render_surface()->screen_space_transform(), current_layer->drawable_content_rect()))
+            return true;
+
+        current_layer = current_layer->parent();
+    }
+
+    // If we have finished walking all ancestors without having already exited, then the point is not clipped by any ancestors.
     return false;
-
-  // Transform the hit test point from screen space to the local space of the
-  // given rect.
-  bool clipped = false;
-  gfx::PointF hit_test_point_in_local_space = MathUtil::ProjectPoint(
-      inverse_local_space_to_screen_space, screen_space_point, &clipped);
-
-  // If ProjectPoint could not project to a valid value, then we assume that
-  // this point doesn't hit this rect.
-  if (clipped)
-    return false;
-
-  return local_space_rect.Contains(hit_test_point_in_local_space);
-}
-
-static bool PointHitsRegion(gfx::PointF screen_space_point,
-                            const gfx::Transform& screen_space_transform,
-                            const Region& layer_space_region,
-                            float layer_content_scale_x,
-                            float layer_content_scale_y) {
-  // If the transform is not invertible, then assume that this point doesn't hit
-  // this region.
-  gfx::Transform inverse_screen_space_transform(
-      gfx::Transform::kSkipInitialization);
-  if (!screen_space_transform.GetInverse(&inverse_screen_space_transform))
-    return false;
-
-  // Transform the hit test point from screen space to the local space of the
-  // given region.
-  bool clipped = false;
-  gfx::PointF hit_test_point_in_content_space = MathUtil::ProjectPoint(
-      inverse_screen_space_transform, screen_space_point, &clipped);
-  gfx::PointF hit_test_point_in_layer_space =
-      gfx::ScalePoint(hit_test_point_in_content_space,
-                      1.f / layer_content_scale_x,
-                      1.f / layer_content_scale_y);
-
-  // If ProjectPoint could not project to a valid value, then we assume that
-  // this point doesn't hit this region.
-  if (clipped)
-    return false;
-
-  return layer_space_region.Contains(
-      gfx::ToRoundedPoint(hit_test_point_in_layer_space));
-}
-
-static bool PointIsClippedBySurfaceOrClipRect(gfx::PointF screen_space_point,
-                                              LayerImpl* layer) {
-  LayerImpl* current_layer = layer;
-
-  // Walk up the layer tree and hit-test any render_surfaces and any layer
-  // clip rects that are active.
-  while (current_layer) {
-    if (current_layer->render_surface() &&
-        !PointHitsRect(
-            screen_space_point,
-            current_layer->render_surface()->screen_space_transform(),
-            current_layer->render_surface()->content_rect()))
-      return true;
-
-    // Note that drawable content rects are actually in target surface space, so
-    // the transform we have to provide is the target surface's
-    // screen_space_transform.
-    LayerImpl* render_target = current_layer->render_target();
-    if (LayerClipsSubtree(current_layer) &&
-        !PointHitsRect(
-            screen_space_point,
-            render_target->render_surface()->screen_space_transform(),
-            current_layer->drawable_content_rect()))
-      return true;
-
-    current_layer = current_layer->parent();
-  }
-
-  // If we have finished walking all ancestors without having already exited,
-  // then the point is not clipped by any ancestors.
-  return false;
-}
-
-LayerImpl* LayerTreeHostCommon::FindLayerThatIsHitByPoint(
-    gfx::PointF screen_space_point,
-    const std::vector<LayerImpl*>& render_surface_layer_list) {
-  LayerImpl* found_layer = NULL;
-
-  typedef LayerIterator<LayerImpl,
-                        std::vector<LayerImpl*>,
-                        RenderSurfaceImpl,
-                        LayerIteratorActions::FrontToBack> LayerIteratorType;
-  LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list);
-
-  for (LayerIteratorType
-           it = LayerIteratorType::Begin(&render_surface_layer_list);
-       it != end;
-       ++it) {
-    // We don't want to consider render_surfaces for hit testing.
-    if (!it.represents_itself())
-      continue;
-
-    LayerImpl* current_layer = (*it);
-
-    gfx::RectF content_rect(gfx::PointF(), current_layer->content_bounds());
-    if (!PointHitsRect(screen_space_point,
-                       current_layer->screen_space_transform(),
-                       content_rect))
-      continue;
-
-    // At this point, we think the point does hit the layer, but we need to walk
-    // up the parents to ensure that the layer was not clipped in such a way
-    // that the hit point actually should not hit the layer.
-    if (PointIsClippedBySurfaceOrClipRect(screen_space_point, current_layer))
-      continue;
-
-    // Skip the HUD layer.
-    if (current_layer == current_layer->layer_tree_impl()->hud_layer())
-      continue;
-
-    found_layer = current_layer;
-    break;
-  }
-
-  // This can potentially return NULL, which means the screen_space_point did
-  // not successfully hit test any layers, not even the root layer.
-  return found_layer;
-}
-
-LayerImpl* LayerTreeHostCommon::FindLayerThatIsHitByPointInTouchHandlerRegion(
-    gfx::PointF screen_space_point,
-    const std::vector<LayerImpl*>& render_surface_layer_list) {
-  LayerImpl* found_layer = NULL;
-
-  typedef LayerIterator<LayerImpl,
-                        std::vector<LayerImpl*>,
-                        RenderSurfaceImpl,
-                        LayerIteratorActions::FrontToBack> LayerIteratorType;
-  LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list);
-
-  for (LayerIteratorType
-           it = LayerIteratorType::Begin(&render_surface_layer_list);
-       it != end;
-       ++it) {
-    // We don't want to consider render_surfaces for hit testing.
-    if (!it.represents_itself())
-      continue;
-
-    LayerImpl* current_layer = (*it);
-
-    if (!LayerHasTouchEventHandlersAt(screen_space_point, current_layer))
-      continue;
-
-    found_layer = current_layer;
-    break;
-  }
-
-  // This can potentially return NULL, which means the screen_space_point did
-  // not successfully hit test any layers, not even the root layer.
-  return found_layer;
-}
-
-bool LayerTreeHostCommon::LayerHasTouchEventHandlersAt(
-    gfx::PointF screen_space_point,
-    LayerImpl* layer_impl) {
-  if (layer_impl->touch_event_handler_region().IsEmpty())
-    return false;
-
-  if (!PointHitsRegion(screen_space_point,
-                       layer_impl->screen_space_transform(),
-                       layer_impl->touch_event_handler_region(),
-                       layer_impl->contents_scale_x(),
-                       layer_impl->contents_scale_y()))
-    return false;
-
-  // At this point, we think the point does hit the touch event handler region
-  // on the layer, but we need to walk up the parents to ensure that the layer
-  // was not clipped in such a way that the hit point actually should not hit
-  // the layer.
-  if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl))
-    return false;
+}
+
+LayerImpl* LayerTreeHostCommon::findLayerThatIsHitByPoint(const gfx::PointF& screenSpacePoint, const std::vector<LayerImpl*>& renderSurfaceLayerList)
+{
+    LayerImpl* foundLayer = 0;
+
+    typedef LayerIterator<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerIteratorActions::FrontToBack> LayerIteratorType;
+    LayerIteratorType end = LayerIteratorType::End(&renderSurfaceLayerList);
+
+    for (LayerIteratorType it = LayerIteratorType::Begin(&renderSurfaceLayerList); it != end; ++it) {
+        // We don't want to consider renderSurfaces for hit testing.
+        if (!it.represents_itself())
+            continue;
+
+        LayerImpl* current_layer = (*it);
+
+        gfx::RectF contentRect(gfx::PointF(), current_layer->content_bounds());
+        if (!pointHitsRect(screenSpacePoint, current_layer->screen_space_transform(), contentRect))
+            continue;
+
+        // At this point, we think the point does hit the layer, but we need to walk up
+        // the parents to ensure that the layer was not clipped in such a way that the
+        // hit point actually should not hit the layer.
+        if (pointIsClippedBySurfaceOrClipRect(screenSpacePoint, current_layer))
+            continue;
+
+        // Skip the HUD layer.
+        if (current_layer == current_layer->layer_tree_impl()->hud_layer())
+            continue;
+
+        foundLayer = current_layer;
+        break;
+    }
+
+    // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
+    return foundLayer;
+}
+
+LayerImpl* LayerTreeHostCommon::findLayerThatIsHitByPointInTouchHandlerRegion(const gfx::PointF& screenSpacePoint, const std::vector<LayerImpl*>& renderSurfaceLayerList)
+{
+    LayerImpl* foundLayer = 0;
+
+    typedef LayerIterator<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerIteratorActions::FrontToBack> LayerIteratorType;
+    LayerIteratorType end = LayerIteratorType::End(&renderSurfaceLayerList);
+
+    for (LayerIteratorType it = LayerIteratorType::Begin(&renderSurfaceLayerList); it != end; ++it) {
+        // We don't want to consider renderSurfaces for hit testing.
+        if (!it.represents_itself())
+            continue;
+
+        LayerImpl* current_layer = (*it);
+
+        if (!layerHasTouchEventHandlersAt(screenSpacePoint, current_layer))
+            continue;
+
+        foundLayer = current_layer;
+        break;
+    }
+
+    // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
+    return foundLayer;
+}
+
+bool LayerTreeHostCommon::layerHasTouchEventHandlersAt(const gfx::PointF& screenSpacePoint, LayerImpl* layerImpl) {
+  if (layerImpl->touch_event_handler_region().IsEmpty())
+      return false;
+
+  if (!pointHitsRegion(screenSpacePoint, layerImpl->screen_space_transform(), layerImpl->touch_event_handler_region(), layerImpl->contents_scale_x(), layerImpl->contents_scale_y()))
+     return false;;
+
+  // At this point, we think the point does hit the touch event handler region on the layer, but we need to walk up
+  // the parents to ensure that the layer was not clipped in such a way that the
+  // hit point actually should not hit the layer.
+  if (pointIsClippedBySurfaceOrClipRect(screenSpacePoint, layerImpl))
+     return false;
 
   return true;
 }
 }  // namespace cc