Let only the root layer paint root background

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 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 2446 matching lines @@
     if (graphicsLayerPaintingPhase & GraphicsLayerPaintMask)
         paintLayerFlags |= PaintLayerPaintingCompositingMaskPhase;
     if (graphicsLayerPaintingPhase & GraphicsLayerPaintChildClippingMask)
         paintLayerFlags |= PaintLayerPaintingChildClippingMaskPhase;
     if (graphicsLayerPaintingPhase & GraphicsLayerPaintOverflowContents)
         paintLayerFlags |= PaintLayerPaintingOverflowContents;
     if (graphicsLayerPaintingPhase & GraphicsLayerPaintCompositedScroll)
         paintLayerFlags |= PaintLayerPaintingCompositingScrollingPhase;
 
     if (graphicsLayer == m_backgroundLayer.get())
-        paintLayerFlags |= (PaintLayerPaintingRootBackgroundOnly | PaintLayerPaintingCompositingForegroundPhase); // Need PaintLayerPaintingCompositingForegroundPhase to walk child layers.
+        paintLayerFlags |= PaintLayerPaintingRootBackgroundOnly;
     else if (compositor()->fixedRootBackgroundLayer() && m_owningLayer.isRootLayer())
         paintLayerFlags |= PaintLayerPaintingSkipRootBackground;
 
     if (graphicsLayer == m_graphicsLayer.get()
         || graphicsLayer == m_foregroundLayer.get()
         || graphicsLayer == m_backgroundLayer.get()
         || graphicsLayer == m_maskLayer.get()
         || graphicsLayer == m_childClippingMaskLayer.get()
         || graphicsLayer == m_scrollingContentsLayer.get()) {
 
@@ skipping 225 matching lines @@
     } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
         name = "Scrolling Contents Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink