[DevTools] Use device metrics emulation implemented in content.

public/web/WebDevToolsAgent.h

 /*
  * Copyright (C) 2009 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 56 matching lines @@
 
     virtual void inspectElementAt(const WebPoint&) = 0;
     virtual void setProcessId(long) = 0;
     virtual void setLayerTreeId(int) = 0;
 
     virtual void didBeginFrame() = 0;
     virtual void didCancelFrame() = 0;
     virtual void willComposite() = 0;
     virtual void didComposite() = 0;
 
+    virtual void setDeviceEmulationScales(bool enabled, float deviceScaleFactor, float rootLayerScale) = 0;
+
     // Exposed for TestRunner.
     virtual void evaluateInWebInspector(long callId, const WebString& script) = 0;
 
     class MessageDescriptor {
     public:
         virtual ~MessageDescriptor() { }
         virtual WebDevToolsAgent* agent() = 0;
         virtual WebString message() = 0;
     };
     // Asynchronously request debugger to pause immediately and run the command.
     WEBKIT_EXPORT static void interruptAndDispatch(MessageDescriptor*);
     WEBKIT_EXPORT static bool shouldInterruptForMessage(const WebString&);
     WEBKIT_EXPORT static void processPendingMessages();
 
 };
 
 } // namespace WebKit
 
 #endif