Extract subpixel offsets from composited layer transforms when possible.

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 221 matching lines @@
       layer == data_from_ancestor.overscroll_elasticity_layer;
   const bool is_scrollable = layer->scrollable();
   const bool is_fixed = layer->position_constraint().is_fixed_position();
 
   const bool has_significant_transform =
       !layer->transform().IsIdentityOr2DTranslation();
 
   const bool has_potentially_animated_transform =
       layer->HasPotentiallyRunningTransformAnimation();
 
+    LOG(ERROR) << "AddTransformNodeIfNeeded: " << layer;
+
+
   // A transform node is needed even for a finished animation, since differences
   // in the timing of animation state updates can mean that an animation that's
   // in the Finished state at tree-building time on the main thread is still in
   // the Running state right after commit on the compositor thread.
   const bool has_any_transform_animation =
       layer->HasAnyAnimationTargetingProperty(TargetProperty::TRANSFORM);
 
   const bool has_surface = created_render_surface;
 
   // A transform node is needed to change the render target for subtree when
@@ skipping 63 matching lines @@
                                   layer->transform().To2dTranslation();
     gfx::Vector2dF source_to_parent;
     if (source_index != parent_index) {
       gfx::Transform to_parent;
       data_from_ancestor.transform_tree->ComputeTransform(
           source_index, parent_index, &to_parent);
       source_to_parent = to_parent.To2dTranslation();
     }
     layer->set_offset_to_transform_parent(source_offset + source_to_parent +
                                           local_offset);
+    LOG(ERROR) << "subpixel offset: " << layer->subpixel_offset_.ToString();
+    LOG(ERROR) << "set_offset_to_transform_parent: " << layer << ": " << layer->offset_to_transform_parent().ToString() << ": " << layer->transform().To2dTranslation().ToString();
     layer->set_should_flatten_transform_from_property_tree(
         data_from_ancestor.should_flatten);
     layer->SetTransformTreeIndex(parent_index);
     if (layer->mask_layer())
       layer->mask_layer()->SetTransformTreeIndex(parent_index);
     return false;
   }
 
   data_for_children->transform_tree->Insert(TransformNode(), parent_index);
 
@@ skipping 664 matching lines @@
   if (SkColorGetA(color) != 255)
     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);
 }
 
 }  // namespace cc