[PresentationAPI] Added on-session-message handler.

content/renderer/presentation/presentation_dispatcher.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 CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_
 #define CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_
 
 #include "base/compiler_specific.h"
 #include "content/common/content_export.h"
 #include "content/common/presentation/presentation_service.mojom.h"
@@ skipping 40 matching lines @@
       bool available);
   void OnSessionCreated(
       blink::WebPresentationSessionClientCallbacks* callback,
       presentation::PresentationSessionInfoPtr session_info,
       presentation::PresentationErrorPtr error);
   void OnDefaultSessionStarted(
       presentation::PresentationSessionInfoPtr session_info);
   void OnSessionStateChange(
       presentation::PresentationSessionInfoPtr session_info,
       presentation::PresentationSessionState session_state);
+  void OnSessionTextMessageReceived(
+      presentation::PresentationSessionInfoPtr session_info,
+      const std::string& message);
 
   void ConnectToPresentationServiceIfNeeded();
 
   void DoUpdateAvailableChangeWatched(
       const std::string& presentation_url,
       bool watched);
 
   // Used as a weak reference. Can be null since lifetime is bound to the frame.
   blink::WebPresentationController* controller_;
   presentation::PresentationServicePtr presentation_service_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_