Make IsSolidColor() a property on CC scrollbar layers.

cc/layers/scrollbar_layer_impl.h

Index: cc/layers/scrollbar_layer_impl.h
diff --git a/cc/layers/scrollbar_layer_impl.h b/cc/layers/scrollbar_layer_impl.h
index dbbbe480e453fc014c7299deb10e7ef181d7b4de..442a189969083d4fb71ae1bf1e7844d199b4872d 100644
--- a/cc/layers/scrollbar_layer_impl.h
+++ b/cc/layers/scrollbar_layer_impl.h
@@ -19,7 +19,8 @@ class CC_EXPORT ScrollbarLayerImpl : public LayerImpl {
   static scoped_ptr<ScrollbarLayerImpl> Create(
       LayerTreeImpl* tree_impl,
       int id,
-      ScrollbarOrientation orientation);
+      ScrollbarOrientation orientation,
+      bool is_solid_color);
   virtual ~ScrollbarLayerImpl();
 
   // LayerImpl implementation.
@@ -39,6 +40,8 @@ class CC_EXPORT ScrollbarLayerImpl : public LayerImpl {
   void set_scroll_layer_id(int id) { scroll_layer_id_ = id; }
 
   ScrollbarOrientation Orientation() const;
+  bool IsSolidColor() const;
+  void set_is_solid_color(bool is_solid_color);
   float CurrentPos() const;
   int Maximum() const;
 
@@ -75,7 +78,8 @@ class CC_EXPORT ScrollbarLayerImpl : public LayerImpl {
  protected:
   ScrollbarLayerImpl(LayerTreeImpl* tree_impl,
                      int id,
-                     ScrollbarOrientation orientation);
+                     ScrollbarOrientation orientation,
+                     bool is_solid_color);
 
  private:
   virtual const char* LayerTypeAsString() const OVERRIDE;
@@ -106,6 +110,7 @@ class CC_EXPORT ScrollbarLayerImpl : public LayerImpl {
   bool enabled_;
   bool is_custom_scrollbar_;
   bool is_overlay_scrollbar_;
+  bool is_solid_color_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollbarLayerImpl);
 };