Make IsSolidColor() a property on CC scrollbar layers.

cc/layers/scrollbar_layer.h

 // Copyright 2012 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_SCROLLBAR_LAYER_H_
 #define CC_LAYERS_SCROLLBAR_LAYER_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/input/scrollbar.h"
 #include "cc/layers/contents_scaling_layer.h"
 #include "cc/layers/scrollbar_theme_painter.h"
 #include "cc/resources/layer_updater.h"
 
 namespace cc {
 class CachingBitmapContentLayerUpdater;
 class ResourceUpdateQueue;
 class ScrollbarThemeComposite;
 
 class CC_EXPORT ScrollbarLayer : public ContentsScalingLayer {
  public:
   virtual scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl)
       OVERRIDE;
 
   static scoped_refptr<ScrollbarLayer> Create(
       scoped_ptr<Scrollbar> scrollbar,
-      int scroll_layer_id);
+      int scroll_layer_id,
+      bool is_solid_color);
 
   int scroll_layer_id() const { return scroll_layer_id_; }
   void SetScrollLayerId(int id);
 
   virtual bool OpacityCanAnimateOnImplThread() const OVERRIDE;
 
   ScrollbarOrientation Orientation() const;
+  bool IsSolidColor() const;
 
   // Layer interface
   virtual void SetTexturePriorities(const PriorityCalculator& priority_calc)
       OVERRIDE;
   virtual void Update(ResourceUpdateQueue* queue,
                       const OcclusionTracker* occlusion,
                       RenderingStats* stats) OVERRIDE;
   virtual void SetLayerTreeHost(LayerTreeHost* host) OVERRIDE;
   virtual void PushPropertiesTo(LayerImpl* layer) OVERRIDE;
   virtual void CalculateContentsScale(float ideal_contents_scale,
                                       float device_scale_factor,
                                       float page_scale_factor,
                                       bool animating_transform_to_screen,
                                       float* contents_scale_x,
                                       float* contents_scale_y,
                                       gfx::Size* content_bounds) OVERRIDE;
 
   virtual ScrollbarLayer* ToScrollbarLayer() OVERRIDE;
 
  protected:
   ScrollbarLayer(scoped_ptr<Scrollbar> scrollbar,
-                 int scroll_layer_id);
+                 int scroll_layer_id,
+                 bool is_solid_color);
   virtual ~ScrollbarLayer();
 
  private:
   void UpdatePart(CachingBitmapContentLayerUpdater* painter,
                   LayerUpdater::Resource* resource,
                   gfx::Rect rect,
                   ResourceUpdateQueue* queue,
                   RenderingStats* stats);
   void CreateUpdaterIfNeeded();
   gfx::Rect ScrollbarLayerRectToContentRect(gfx::Rect layer_rect) const;
   gfx::Rect OriginThumbRect() const;
 
   bool is_dirty() const { return !dirty_rect_.IsEmpty(); }
 
   int MaxTextureSize();
   float ClampScaleToMaxTextureSize(float scale);
 
   scoped_ptr<Scrollbar> scrollbar_;
 
   int thumb_thickness_;
   int thumb_length_;
   gfx::Rect track_rect_;
   int scroll_layer_id_;
+  bool is_solid_color_;
 
   unsigned texture_format_;
 
   gfx::RectF dirty_rect_;
 
   scoped_refptr<CachingBitmapContentLayerUpdater> track_updater_;
   scoped_refptr<CachingBitmapContentLayerUpdater> thumb_updater_;
 
   // All the parts of the scrollbar except the thumb
   scoped_ptr<LayerUpdater::Resource> track_;
   scoped_ptr<LayerUpdater::Resource> thumb_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollbarLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_SCROLLBAR_LAYER_H_