Implementation of device metrics emulation in render view.

content/renderer/devtools/devtools_agent.h

Index: content/renderer/devtools/devtools_agent.h
diff --git a/content/renderer/devtools/devtools_agent.h b/content/renderer/devtools/devtools_agent.h
index 4ac22db97f9c3095f96b23c171f451cb6358affb..9860ed7a1af9c5bb5981a74c312f70569f1958f4 100644
--- a/content/renderer/devtools/devtools_agent.h
+++ b/content/renderer/devtools/devtools_agent.h
@@ -53,6 +53,11 @@ class DevToolsAgent : public RenderViewObserver,
   virtual void clearBrowserCookies();
   virtual void visitAllocatedObjects(AllocatedObjectVisitor* visitor);
   virtual void setTraceEventCallback(TraceEventCallback cb);
+  virtual void enableDeviceEmulation(
+      const WebKit::WebSize& device_size,
+      const WebKit::WebRect& view_rect, float device_scale_factor,
+      bool fit_to_view);
+  virtual void disableDeviceEmulation();
 
   void OnAttach();
   void OnReattach(const std::string& agent_state);