[MediaRouter] Update MR-2-Extension's PostMessage to return boolean.

chrome/browser/media/router/media_router.h

 // Copyright 2015 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_MEDIA_ROUTER_MEDIA_ROUTER_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 17 matching lines @@
 // request failed.
 using MediaRouteResponseCallback =
     base::Callback<void(scoped_ptr<MediaRoute>, const std::string&)>;
 
 // An interface for handling resources related to media routing.
 // Responsible for registering observers for receiving sink availability
 // updates, handling route requests/responses, and operating on routes (e.g.
 // posting messages or closing).
 class MediaRouter {
  public:
+  using SendRouteMessageCallback = base::Callback<void(bool sent)>;
+
   virtual ~MediaRouter() {}
 
   // Creates a media route from |source_id| to |sink_id|.
   // |callback| is invoked with a response indicating success or failure.
   virtual void CreateRoute(const MediaSource::Id& source_id,
                            const MediaSink::Id& sink_id,
                            const MediaRouteResponseCallback& callback) = 0;
 
   // Closes the media route specified by |route_id|.
   virtual void CloseRoute(const MediaRoute::Id& route_id) = 0;
 
   // Posts |message| to a MediaSink connected via MediaRoute with |route_id|.
   // TODO(imcheng): Support additional data types: Blob, ArrayBuffer,
   // ArrayBufferView.
-  virtual void PostMessage(const MediaRoute::Id& route_id,
-                           const std::string& message) = 0;
+  virtual void SendRouteMessage(const MediaRoute::Id& route_id,
+                                const std::string& message,
+                                const SendRouteMessageCallback& callback) = 0;
 
   // Clears the issue with the id |issue_id|.
   virtual void ClearIssue(const Issue::Id& issue_id) = 0;
 
   // Receives updates from a MediaRouter instance.
   class Delegate {
    public:
     // Called when there is a message from a route.
     // |route_id|: The route ID.
     // |message|: The message.
@@ skipping 42 matching lines @@
   // in undefined behavior.
   virtual void AddIssuesObserver(IssuesObserver* observer) = 0;
 
   // Removes the IssuesObserver |observer|.
   virtual void RemoveIssuesObserver(IssuesObserver* observer) = 0;
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_H_