Releasing Track & Thumb UIResources based on their Geometry

cc/layers/painted_scrollbar_layer.h

Index: cc/layers/painted_scrollbar_layer.h
diff --git a/cc/layers/painted_scrollbar_layer.h b/cc/layers/painted_scrollbar_layer.h
index cd6a0460a43fa0f7cc1318df72c84b8564f6153a..6d3c9d308cbe3049b0d7e51ebeb900adb5e87787 100644
--- a/cc/layers/painted_scrollbar_layer.h
+++ b/cc/layers/painted_scrollbar_layer.h
@@ -59,6 +59,7 @@ class CC_EXPORT PaintedScrollbarLayer : public ScrollbarLayerInterface,
     return thumb_resource_.get() ? thumb_resource_->id() : 0;
   }
   void UpdateThumbAndTrackGeometry();
+  void ReleaseThumbAndTrackUIResourcesIfNecessary();
 
  private:
   gfx::Rect ScrollbarLayerRectToContentRect(const gfx::Rect& layer_rect) const;