[DevTools] Use device metrics emulation implemented in content.

Source/core/inspector/InspectorPageAgent.h

 /*
  * Copyright (C) 2011 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 185 matching lines @@
     InspectorOverlay* m_overlay;
     long m_lastScriptIdentifier;
     String m_pendingScriptToEvaluateOnLoadOnce;
     String m_scriptToEvaluateOnLoadOnce;
     String m_pendingScriptPreprocessor;
     String m_scriptPreprocessorSource;
     HashMap<Frame*, String> m_frameToIdentifier;
     HashMap<String, Frame*> m_identifierToFrame;
     HashMap<DocumentLoader*, String> m_loaderToIdentifier;
     bool m_enabled;
-    bool m_isFirstLayoutAfterOnLoad;
     bool m_geolocationOverridden;
     bool m_ignoreScriptsEnabledNotification;
     bool m_didForceCompositingMode;
     RefPtr<GeolocationPosition> m_geolocationPosition;
     RefPtr<GeolocationPosition> m_platformGeolocationPosition;
     RefPtr<DeviceOrientationData> m_deviceOrientation;
 };
 
 
 } // namespace WebCore
 
 
 #endif // !defined(InspectorPagerAgent_h)