Add development Blink setting for impl-side rubber-banding

Source/core/rendering/compositing/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 883 matching lines @@
 
 bool RenderLayerCompositor::requiresScrollCornerLayer() const
 {
     FrameView* view = m_renderView.frameView();
     return shouldCompositeOverflowControls(view) && view->isScrollCornerVisible();
 }
 
 void RenderLayerCompositor::updateOverflowControlsLayers()
 {
 #if USE(RUBBER_BANDING)
-    if (m_renderView.frame()->isLocalRoot()) {
+    if (m_renderView.frame()->isLocalRoot() && !m_renderView.document().settings()->rubberBandingOnCompositorThread()) {
         if (!m_layerForOverhangShadow) {
             m_layerForOverhangShadow = GraphicsLayer::create(graphicsLayerFactory(), this);
             OverscrollTheme::theme()->setUpOverhangShadowLayer(m_layerForOverhangShadow.get());
             OverscrollTheme::theme()->updateOverhangShadowLayer(m_layerForOverhangShadow.get(), m_rootContentLayer.get());
             m_scrollLayer->addChild(m_layerForOverhangShadow.get());
         }
     } else {
         ASSERT(!m_layerForOverhangShadow);
     }
 #endif
@@ skipping 273 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "LocalFrame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink