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

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 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:
  *
  *     * 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 3806 matching lines @@
   DCHECK(document);
 
   // Get the outer viewport scroll layer.
   GraphicsLayer* layoutViewportScrollLayer =
       page()->frameHost().globalRootScrollerController().rootScrollerLayer();
   WebLayer* layoutViewportWebLayer =
       layoutViewportScrollLayer ? layoutViewportScrollLayer->platformLayer()
                                 : nullptr;
 
   VisualViewport& visualViewport = page()->frameHost().visualViewport();
+
+  // TODO(bokan): This was moved here from when registerViewportLayers was a
+  // part of VisualViewport and maybe doesn't belong here. See comment inside
+  // the mehtod.
+  visualViewport.setScrollLayerOnScrollbars(layoutViewportWebLayer);
+
   m_layerTreeView->registerViewportLayers(
       visualViewport.overscrollElasticityLayer()->platformLayer(),
       visualViewport.pageScaleLayer()->platformLayer(),
       visualViewport.scrollLayer()->platformLayer(), layoutViewportWebLayer);
 }
 
 void WebViewImpl::setRootGraphicsLayer(GraphicsLayer* graphicsLayer) {
   if (!m_layerTreeView)
     return;
 
@@ skipping 323 matching lines @@
   if (focusedFrame->localFrameRoot() != mainFrameImpl()->frame())
     return nullptr;
   return focusedFrame;
 }
 
 LocalFrame* WebViewImpl::focusedLocalFrameAvailableForIme() const {
   return m_imeAcceptEvents ? focusedLocalFrameInWidget() : nullptr;
 }
 
 }  // namespace blink