Revert of Remove indirection: setup scrollbar scroll layers in the scrollbar constructor

third_party/WebKit/Source/core/frame/VisualViewport.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 435 matching lines @@
   int thumbThickness = theme.thumbThickness();
   int scrollbarThickness = theme.scrollbarThickness(RegularScrollbar);
   int scrollbarMargin = theme.scrollbarMargin();
 
   if (!webScrollbarLayer) {
     ScrollingCoordinator* coordinator =
         frameHost().page().scrollingCoordinator();
     ASSERT(coordinator);
     ScrollbarOrientation webcoreOrientation =
         isHorizontal ? HorizontalScrollbar : VerticalScrollbar;
-    WebLayer* scrollLayer = layerForScrolling()->platformLayer();
     webScrollbarLayer = coordinator->createSolidColorScrollbarLayer(
-        webcoreOrientation, thumbThickness, scrollbarMargin, false,
-        scrollLayer);
+        webcoreOrientation, thumbThickness, scrollbarMargin, false);
 
     // The compositor will control the scrollbar's visibility. Set to invisible
     // by default so scrollbars don't show up in layout tests.
     webScrollbarLayer->layer()->setOpacity(0);
     scrollbarGraphicsLayer->setContentsToPlatformLayer(
         webScrollbarLayer->layer());
     scrollbarGraphicsLayer->setDrawsContent(false);
   }
 
   int xPosition = isHorizontal ? 0
@@ skipping 10 matching lines @@
   int height = isHorizontal ? scrollbarThickness
                             : m_innerViewportContainerLayer->size().height() -
                                   scrollbarThickness;
 
   // Use the GraphicsLayer to position the scrollbars.
   scrollbarGraphicsLayer->setPosition(IntPoint(xPosition, yPosition));
   scrollbarGraphicsLayer->setSize(FloatSize(width, height));
   scrollbarGraphicsLayer->setContentsRect(IntRect(0, 0, width, height));
 }
 
+void VisualViewport::setScrollLayerOnScrollbars(WebLayer* scrollLayer) const {
+  // TODO(bokan): This is currently done while registering viewport layers
+  // with the compositor but could it actually be done earlier, like in
+  // setupScrollbars? Then we wouldn't need this method.
+  m_webOverlayScrollbarHorizontal->setScrollLayer(scrollLayer);
+  m_webOverlayScrollbarVertical->setScrollLayer(scrollLayer);
+}
+
 bool VisualViewport::visualViewportSuppliesScrollbars() const {
   return frameHost().page().settings().getViewportEnabled();
 }
 
 bool VisualViewport::scrollAnimatorEnabled() const {
   return frameHost().page().settings().getScrollAnimatorEnabled();
 }
 
 HostWindow* VisualViewport::getHostWindow() const {
   return &frameHost().page().chromeClient();
@@ skipping 349 matching lines @@
   } else if (graphicsLayer == m_rootTransformLayer.get()) {
     name = "Root Transform Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink