Let only the root layer paint root background

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

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 263634c96d5b147266a773ec803c62f833cc8457..10d8978f2936e5bf24b79405c6203584d8490139 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2464,7 +2464,7 @@ void CompositedLayerMapping::paintContents(const GraphicsLayer* graphicsLayer, G
         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;