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

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"
 #include "modules/presentation/PresentationSession.h"
 #include "platform/heap/Handle.h"
 #include "platform/heap/Heap.h"
 
 namespace WTF {
 class String;
 } // namespace WTF
 
 namespace blink {
 
 class LocalFrame;
 class PresentationController;
 class ScriptState;
+class WebPresentationSessionClient;
 
 // Implements the main entry point of the Presentation API corresponding to the Presentation.idl
 // See https://w3c.github.io/presentation-api/#navigatorpresentation for details.
 class Presentation final
     : public RefCountedGarbageCollectedEventTargetWithInlineData<Presentation>
     , public DOMWindowProperty {
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCountedGarbageCollected<Presentation>);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Presentation);
     DEFINE_WRAPPERTYPEINFO();
 public:
@@ skipping 24 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*);
 
     // Adds a session to the open sessions list.
     void registerSession(PresentationSession*);
 
+    // Returns the session that matches the WebPresentationSessionClient or null.
+    PresentationSession* findSession(WebPresentationSessionClient*);
+
 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();
 
     // 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