[PresentationAPI] Added on-session-text-message handler.

Source/modules/presentation/Presentation.h

 // Copyright 2014 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 Presentation_h
 #define Presentation_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "core/events/EventTarget.h"
 #include "core/frame/DOMWindowProperty.h"
@@ skipping 49 matching lines @@
     void didChangeAvailability(bool available);
     // Queried by the controller if |availablechange| event has any listeners.
     bool isAvailableChangeWatched() const;
 
     // Called when the |defaultsessionstart| event needs to be fired.
     void didStartDefaultSession(PresentationSession*);
 
     // Called when the |onstatechange| event needs to be fired to the right session.
     void didChangeSessionState(WebPresentationSessionClient*, WebPresentationSessionState);
 
+    // Called when the |onmessage| event needs to be fired to the right session.
+    void didReceiveSessionTextMessage(WebPresentationSessionClient*, const String& message);
+
     // Adds a session to the open sessions list.
     void registerSession(PresentationSession*);
 
 private:
     explicit Presentation(LocalFrame*);
 
     // Returns the |PresentationController| object associated with the frame |Presentation| corresponds to.
     // Can return |nullptr| if the frame is detached from the document.
     PresentationController* presentationController();
 
     // Returns the session that matches the WebPresentationSessionClient or null.
     PresentationSession* findSession(WebPresentationSessionClient*);
 
     // The session object provided to the presentation page. Not supported.
     Member<PresentationSession> m_session;
 
     // The sessions opened for this frame.
     HeapHashSet<Member<PresentationSession>> m_openSessions;
 };
 
 } // namespace blink
 
 #endif // Presentation_h