Plumb preferred raster scale for background images from Blink to cc layers.

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 429 matching lines @@
     was_ever_ready_since_last_transform_animation_ = was_ready;
   }
 
   void NoteLayerPropertyChanged();
 
   void SetHasWillChangeTransformHint(bool has_will_change);
   bool has_will_change_transform_hint() const {
     return has_will_change_transform_hint_;
   }
 
+  void SetPreferredRasterScale(float raster_scale);
+  bool has_preferred_raster_scale() { return has_preferred_raster_scale_; }
+  float preferred_raster_scale() const { return preferred_raster_scale_; }
+  void ClearPreferredRasterScale();
+
   AnimationHost* GetAnimationHost() const;
 
   ElementListType GetElementTypeForAnimation() const;
 
  protected:
   LayerImpl(LayerTreeImpl* layer_impl,
             int id,
             scoped_refptr<SyncedScrollOffset> scroll_offset);
   LayerImpl(LayerTreeImpl* layer_impl, int id);
 
@@ skipping 96 matching lines @@
 
   // Group of properties that need to be computed based on the layer tree
   // hierarchy before layers can be drawn.
   DrawProperties draw_properties_;
   PerformanceProperties<LayerImpl> performance_properties_;
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
       owned_debug_info_;
   base::trace_event::ConvertableToTraceFormat* debug_info_;
   std::unique_ptr<RenderSurfaceImpl> render_surface_;
+  float preferred_raster_scale_;
 
+  bool has_preferred_raster_scale_ : 1;
   bool scrolls_drawn_descendant_ : 1;
   bool has_will_change_transform_hint_ : 1;
   bool needs_push_properties_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_