Add Frame::isMainFrame and deploy it

Source/core/rendering/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 149 matching lines @@
     : m_owningLayer(layer)
     , m_animationProvider(adoptPtr(new WebAnimationProvider))
     , m_artificiallyInflatedBounds(false)
     , m_boundsConstrainedByClipping(false)
     , m_isMainFrameRenderViewLayer(false)
     , m_requiresOwnBackingStoreForIntrinsicReasons(true)
     , m_requiresOwnBackingStoreForAncestorReasons(true)
     , m_canCompositeFilters(false)
     , m_backgroundLayerPaintsFixedRootBackground(false)
 {
-    if (layer->isRootLayer()) {
-        Frame& frame = toRenderView(renderer())->frameView()->frame();
-        Page* page = frame.page();
-        if (page && page->mainFrame() == &frame) {
-            m_isMainFrameRenderViewLayer = true;
-        }
-    }
+    if (layer->isRootLayer() && renderer()->frame()->isMainFrame())
+        m_isMainFrameRenderViewLayer = true;
 
     createPrimaryGraphicsLayer();
 }
 
 CompositedLayerMapping::~CompositedLayerMapping()
 {
     updateClippingLayers(false, false);
     updateOverflowControlsLayers(false, false, false);
     updateForegroundLayer(false);
     updateBackgroundLayer(false);
@@ skipping 1838 matching lines @@
     } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
         name = "Scrolling Contents Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore