[DevTools] Make sendMessageToBackend one of embedder messages.

chrome/browser/devtools/devtools_embedder_message_dispatcher.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DEVTOOLS_DEVTOOLS_EMBEDDER_MESSAGE_DISPATCHER_H_
 #define CHROME_BROWSER_DEVTOOLS_DEVTOOLS_EMBEDDER_MESSAGE_DISPATCHER_H_
 
 #include <map>
 #include <string>
 
@@ skipping 46 matching lines @@
                               const std::string& query) = 0;
     virtual void SetWhitelistedShortcuts(const std::string& message) = 0;
     virtual void ZoomIn() = 0;
     virtual void ZoomOut() = 0;
     virtual void ResetZoom() = 0;
     virtual void OpenUrlOnRemoteDeviceAndInspect(const std::string& browser_id,
                                                  const std::string& url) = 0;
 
     virtual void SetDeviceCountUpdatesEnabled(bool enabled) = 0;
     virtual void SetDevicesUpdatesEnabled(bool enabled) = 0;
+    virtual void SendMessageToBrowser(const std::string& message) = 0;
   };
 
   virtual ~DevToolsEmbedderMessageDispatcher() {}
   virtual bool Dispatch(const std::string& method,
                         const base::ListValue* params,
                         std::string* error) = 0;
 
   static DevToolsEmbedderMessageDispatcher* createForDevToolsFrontend(
       Delegate* delegate);
 };
 
 #endif  // CHROME_BROWSER_DEVTOOLS_DEVTOOLS_EMBEDDER_MESSAGE_DISPATCHER_H_