[DevTools] Use device metrics emulation implemented in content.

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 2413 matching lines @@
         m_rootContentLayer->setMasksToBounds(true);
     }
 
     if (!m_overflowControlsHostLayer) {
         ASSERT(!m_scrollLayer);
         ASSERT(!m_containerLayer);
 
         // Create a layer to host the clipping layer and the overflow controls layers.
         m_overflowControlsHostLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
 
-        // Create a clipping layer if this is an iframe
+        // Create a clipping layer if this is an iframe or settings require to clip.
         m_containerLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
-        if (!isMainFrame())
-            m_containerLayer->setMasksToBounds(true);
+        bool containerMasksToBounds = !isMainFrame();
+        if (Settings* settings = m_renderView->document().settings()) {
+            if (settings->rootLayerClipsContent())
+                containerMasksToBounds = true;
+        }
+        m_containerLayer->setMasksToBounds(containerMasksToBounds);
 
         m_scrollLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
         if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
             scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(m_scrollLayer.get(), true);
 
         // Hook them up
         m_overflowControlsHostLayer->addChild(m_containerLayer.get());
         m_containerLayer->addChild(m_scrollLayer.get());
         m_scrollLayer->addChild(m_rootContentLayer.get());
 
@@ skipping 336 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore