[PresentationAPI] Plumbing |onstatechange| event for the PresentationSession from Blink to platform/

Source/modules/presentation/PresentationController.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 PresentationController_h
 #define PresentationController_h
 
 #include "core/frame/FrameDestructionObserver.h"
 #include "modules/presentation/Presentation.h"
 #include "platform/Supplementable.h"
@@ skipping 25 matching lines @@
 
     static void provideTo(LocalFrame&, WebPresentationClient*);
 
     // Implementation of HeapSupplement.
     DECLARE_VIRTUAL_TRACE();
 
     // Implementation of WebPresentationController.
     virtual void didChangeAvailability(bool available) override;
     virtual bool isAvailableChangeWatched() const override;
     virtual void didStartDefaultSession(WebPresentationSessionClient*) override;
+    virtual void didChangeSessionState(WebPresentationSessionClient*, WebPresentationSessionClient::SessionState) override;
 
     // Called when the first listener was added to or the last listener was removed from the
     // |availablechange| event.
     void updateAvailableChangeWatched(bool watched);
 
     // Called when the frame wants to start a new presentation.
     void startSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks*);
 
     // Called when the frame wants to join an existing presentation.
     void joinSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks*);
@@ skipping 10 matching lines @@
     // Implementation of FrameDestructionObserver.
     virtual void willDetachFrameHost() override;
 
     WebPresentationClient* m_client;
     PersistentWillBeMember<Presentation> m_presentation;
 };
 
 } // namespace blink
 
 #endif // PresentationController_h