Set root clip layer not to maskToBounds.

Source/core/rendering/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 2379 matching lines @@
         m_overflowControlsHostLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
 #ifndef NDEBUG
         m_overflowControlsHostLayer->setName("overflow controls host");
 #endif
 
         // Create a clipping layer if this is an iframe
         m_clipLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
 #ifndef NDEBUG
         m_clipLayer->setName("frame clipping");
 #endif
-        m_clipLayer->setMasksToBounds(true);
+        if (expectedAttachment != RootLayerAttachedViaChromeClient)

[trchen, 2013/07/11 01:11:16]

if (!isMainFrame())
sounds more straightforward IMO.

[aelias_OOO_until_Jul13, 2013/07/11 03:46:17]

Done.

+            m_clipLayer->setMasksToBounds(true);
 
         m_scrollLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
 #ifndef NDEBUG
         m_scrollLayer->setName("frame scrolling");
 #endif
         if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
             scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(m_scrollLayer.get(), true);
 
         // Hook them up
         m_overflowControlsHostLayer->addChild(m_clipLayer.get());
@@ skipping 331 matching lines @@
     info.addMember(m_layerForScrollCorner, "layerForScrollCorner");
 #if ENABLE(RUBBER_BANDING)
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
     info.addMember(m_layerForTopOverhangArea, "layerForTopOverhangArea");
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
 #endif
 }
 
 } // namespace WebCore