Extract subpixel offsets from composited layer transforms when possible.

cc/layers/layer_impl.h

 // 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 451 matching lines @@
     touch_event_handler_region_ = region;
   }
   const Region& touch_event_handler_region() const {
     return touch_event_handler_region_;
   }
 
   void SetDoubleSided(bool double_sided);
   bool double_sided() const { return double_sided_; }
 
   void SetTransform(const gfx::Transform& transform);
+  void SetSubpixelOffset(const gfx::Vector2dF& subpixel_offset) { subpixel_offset_ = subpixel_offset; }
   const gfx::Transform& transform() const { return transform_; }
   bool TransformIsAnimating() const;
   bool HasPotentiallyRunningTransformAnimation() const;
   bool TransformIsAnimatingOnImplOnly() const;
   bool HasOnlyTranslationTransforms() const;
   bool AnimationsPreserveAxisAlignment() const;
   void SetTransformAndInvertibility(const gfx::Transform& transform,
                                     bool transform_is_invertible);
   bool transform_is_invertible() const { return transform_is_invertible_; }
 
@@ skipping 245 matching lines @@
 
  protected:
   friend class TreeSynchronizer;
 
   // Layers that share a sorting context id will be sorted together in 3d
   // space.  0 is a special value that means this layer will not be sorted and
   // will be drawn in paint order.
   int sorting_context_id_;
 
   DrawMode current_draw_mode_;
+public:
+  gfx::Vector2dF subpixel_offset_;
 
  private:
   uint64_t element_id_;
   uint32_t mutable_properties_;
   // Rect indicating what was repainted/updated during update.
   // Note that plugin layers bypass this and leave it empty.
   // This is in the layer's space.
   gfx::Rect update_rect_;
 
   // Denotes an area that is damaged and needs redraw. This is in the layer's
@@ skipping 12 matching lines @@
   scoped_ptr<RenderSurfaceImpl> render_surface_;
 
   bool force_render_surface_;
 
   std::vector<FrameTimingRequest> frame_timing_requests_;
   bool frame_timing_requests_dirty_;
   bool layer_or_descendant_is_drawn_;
   // If true, the layer or one of its descendants has a touch handler.
   bool layer_or_descendant_has_touch_handler_;
 
+
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_