Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

third_party/WebKit/public/platform/WebCompositorSupport.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 50 matching lines @@
       WebContentLayerClient*) = 0;
 
   virtual std::unique_ptr<WebExternalTextureLayer> createExternalTextureLayer(
       cc::TextureLayerClient*) = 0;
 
   virtual std::unique_ptr<WebImageLayer> createImageLayer() = 0;
 
   virtual std::unique_ptr<WebScrollbarLayer> createScrollbarLayer(
       std::unique_ptr<WebScrollbar>,
       WebScrollbarThemePainter,
-      std::unique_ptr<WebScrollbarThemeGeometry>) = 0;
+      std::unique_ptr<WebScrollbarThemeGeometry>,
+      WebLayer* scrollLayer) = 0;
 
   virtual std::unique_ptr<WebScrollbarLayer> createOverlayScrollbarLayer(
       std::unique_ptr<WebScrollbar>,
       WebScrollbarThemePainter,
-      std::unique_ptr<WebScrollbarThemeGeometry>) = 0;
+      std::unique_ptr<WebScrollbarThemeGeometry>,
+      WebLayer* scrollLayer) = 0;
 
   virtual std::unique_ptr<WebScrollbarLayer> createSolidColorScrollbarLayer(
       WebScrollbar::Orientation,
       int thumbThickness,
       int trackStart,
-      bool isLeftSideVerticalScrollbar) = 0;
+      bool isLeftSideVerticalScrollbar,
+      WebLayer* scrollLayer) = 0;
 
  protected:
   virtual ~WebCompositorSupport() {}
 };
 }
 
 #endif  // WebCompositorSupport_h