Refactor root element background painting

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.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 1722 matching lines @@
             break;
 
         finalOpacity *= curr->layoutObject()->opacity();
     }
 
     return finalOpacity;
 }
 
 Color CompositedDeprecatedPaintLayerMapping::layoutObjectBackgroundColor() const
 {
-    LayoutObject* backgroundLayoutObject = layoutObject();
-    if (backgroundLayoutObject->isDocumentElement())
-        backgroundLayoutObject = backgroundLayoutObject->layoutObjectForRootBackground();
-
-    return backgroundLayoutObject->resolveColor(CSSPropertyBackgroundColor);
+    return layoutObject()->resolveColor(CSSPropertyBackgroundColor);
 }
 
 void CompositedDeprecatedPaintLayerMapping::updateBackgroundColor()
 {
     m_graphicsLayer->setBackgroundColor(layoutObjectBackgroundColor());
 }
 
 bool CompositedDeprecatedPaintLayerMapping::paintsChildren() const
 {
     if (m_owningLayer.hasVisibleContent() && m_owningLayer.hasNonEmptyChildLayoutObjects())
@@ skipping 587 matching lines @@
     } else if (graphicsLayer == m_scrollingBlockSelectionLayer.get()) {
         name = "Scrolling Block Selection Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink