Undo scroll snaps in to_parent when NeedsSourceToParentUpdate.

cc/trees/property_tree_builder.cc

 // Copyright 2014 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/property_tree_builder.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <set>
@@ skipping 40 matching lines @@
   float page_scale_factor;
   bool in_subtree_of_page_scale_layer;
   bool affected_by_inner_viewport_bounds_delta;
   bool affected_by_outer_viewport_bounds_delta;
   bool should_flatten;
   bool target_is_clipped;
   bool is_hidden;
   uint32_t main_thread_scrolling_reasons;
   bool scroll_tree_parent_created_by_uninheritable_criteria;
   const gfx::Transform* device_transform;
-  gfx::Vector2dF scroll_snap;
   gfx::Transform compound_transform_since_render_target;
   bool axis_align_since_render_target;
   SkColor safe_opaque_background_color;
 };
 
 template <typename LayerType>
 struct DataForRecursionFromChild {
   int num_copy_requests_in_subtree;
 
   DataForRecursionFromChild() : num_copy_requests_in_subtree(0) {}
@@ skipping 461 matching lines @@
       LayerType* source = Parent(layer);
       source_offset += source->offset_to_transform_parent();
       source_index = source->transform_tree_index();
     } else if (!is_fixed) {
       source_offset = transform_parent->offset_to_transform_parent();
     } else {
       source_offset = data_from_ancestor.transform_tree_parent
                           ->offset_to_transform_parent();
       source_index =
           data_from_ancestor.transform_tree_parent->transform_tree_index();
-      source_offset -= data_from_ancestor.scroll_snap;
     }
   }
 
   if (IsContainerForFixedPositionLayers(layer) || is_root) {
     data_for_children->affected_by_inner_viewport_bounds_delta =
         layer == data_from_ancestor.inner_viewport_scroll_layer;
     data_for_children->affected_by_outer_viewport_bounds_delta =
         layer == data_from_ancestor.outer_viewport_scroll_layer;
     if (is_scrollable) {
       DCHECK(!is_root);
       DCHECK(layer->transform().IsIdentity());
       data_for_children->transform_fixed_parent = Parent(layer);
     } else {
       data_for_children->transform_fixed_parent = layer;
     }
   }
   data_for_children->transform_tree_parent = layer;
 
-  if (IsContainerForFixedPositionLayers(layer) || is_fixed)
-    data_for_children->scroll_snap = gfx::Vector2dF();
-
   if (!requires_node) {
     data_for_children->should_flatten |= ShouldFlattenTransform(layer);
     gfx::Vector2dF local_offset = layer->position().OffsetFromOrigin() +
                                   layer->transform().To2dTranslation();
     gfx::Vector2dF source_to_parent;
     if (source_index != parent_index) {
       gfx::Transform to_parent;
       data_from_ancestor.property_trees->transform_tree.ComputeTranslation(
           source_index, parent_index, &to_parent);
       source_to_parent = to_parent.To2dTranslation();
@@ skipping 112 matching lines @@
   node->update_pre_local_transform(TransformOrigin(layer));
 
   node->needs_local_transform_update = true;
   data_from_ancestor.property_trees->transform_tree.UpdateTransforms(node->id);
 
   layer->set_offset_to_transform_parent(gfx::Vector2dF());
 
   // Flattening (if needed) will be handled by |node|.
   layer->set_should_flatten_transform_from_property_tree(false);
 
-  data_for_children->scroll_snap += node->scroll_snap;
-
   node->owner_id = layer->id();
 
   return true;
 }
 
 static inline bool HasPotentialOpacityAnimation(Layer* layer) {
   return HasPotentiallyRunningOpacityAnimation(layer) ||
          layer->OpacityCanAnimateOnImplThread();
 }
 
@@ skipping 764 matching lines @@
     color = SkColorSetA(color, 255);
   BuildPropertyTreesTopLevelInternal(
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,
       elastic_overscroll, page_scale_factor, device_scale_factor, viewport,
       device_transform, property_trees, color);
   property_trees->ResetCachedData();
 }
 
 }  // namespace cc