Refactor cc scrollbar layers to separate solid-color vs desktop.

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index 611bb7c6f8aedec8563e42337fd9290e337ab492..abf6691cb4ad54ab3d33c7558f764bf186c7c22d 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -44,7 +44,7 @@ class LayerTreeImpl;
 class QuadSink;
 class Renderer;
 class ScrollbarAnimationController;
-class ScrollbarLayerImpl;
+class ScrollbarLayerImplBase;
 class Layer;
 
 struct AppendQuadsData;
@@ -128,7 +128,7 @@ class CC_EXPORT LayerImpl : LayerAnimationValueObserver {
 
   virtual void UpdateTilePriorities() {}
 
-  virtual ScrollbarLayerImpl* ToScrollbarLayer();
+  virtual ScrollbarLayerImplBase* ToScrollbarLayerBase();
 
   // Returns true if this layer has content to draw.
   void SetDrawsContent(bool draws_content);
@@ -413,13 +413,13 @@ class CC_EXPORT LayerImpl : LayerAnimationValueObserver {
 
   void SetScrollbarOpacity(float opacity);
 
-  void SetHorizontalScrollbarLayer(ScrollbarLayerImpl* scrollbar_layer);
-  ScrollbarLayerImpl* horizontal_scrollbar_layer() {
+  void SetHorizontalScrollbarLayer(ScrollbarLayerImplBase* scrollbar_layer);
+  ScrollbarLayerImplBase* horizontal_scrollbar_layer() {
     return horizontal_scrollbar_layer_;
   }
 
-  void SetVerticalScrollbarLayer(ScrollbarLayerImpl* scrollbar_layer);
-  ScrollbarLayerImpl* vertical_scrollbar_layer() {
+  void SetVerticalScrollbarLayer(ScrollbarLayerImplBase* scrollbar_layer);
+  ScrollbarLayerImplBase* vertical_scrollbar_layer() {
     return vertical_scrollbar_layer_;
   }
 
@@ -561,8 +561,8 @@ class CC_EXPORT LayerImpl : LayerAnimationValueObserver {
 
   // Weak pointers to this layer's scrollbars, if it has them. Updated during
   // tree synchronization.
-  ScrollbarLayerImpl* horizontal_scrollbar_layer_;
-  ScrollbarLayerImpl* vertical_scrollbar_layer_;
+  ScrollbarLayerImplBase* horizontal_scrollbar_layer_;
+  ScrollbarLayerImplBase* vertical_scrollbar_layer_;
 
   ScopedPtrVector<CopyOutputRequest> copy_requests_;