Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

third_party/WebKit/public/platform/WebCompositorSupport.h

Index: third_party/WebKit/public/platform/WebCompositorSupport.h
diff --git a/third_party/WebKit/public/platform/WebCompositorSupport.h b/third_party/WebKit/public/platform/WebCompositorSupport.h
index 5c3f706aaa1df1a1fad42dc185e13156fe8d99bd..348e8a15986acb7b08e3606b6e04763f10af28b9 100644
--- a/third_party/WebKit/public/platform/WebCompositorSupport.h
+++ b/third_party/WebKit/public/platform/WebCompositorSupport.h
@@ -68,18 +68,21 @@ class WebCompositorSupport {
   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() {}