[PresentationAPI] Ensures only one pending message callback at a time if a frame created multiple s…

content/renderer/presentation/presentation_dispatcher.h

Index: content/renderer/presentation/presentation_dispatcher.h
diff --git a/content/renderer/presentation/presentation_dispatcher.h b/content/renderer/presentation/presentation_dispatcher.h
index fcf22da9393a95d5953fee8f760ccd568e1b1b01..da26d0fd60753e8746bb7e179433d17d60c8d64d 100644
--- a/content/renderer/presentation/presentation_dispatcher.h
+++ b/content/renderer/presentation/presentation_dispatcher.h
@@ -98,6 +98,8 @@ class CONTENT_EXPORT PresentationDispatcher
 
   void UpdateListeningState();
 
+  void StartListenForMessages();
+
   // Used as a weak reference. Can be null since lifetime is bound to the frame.
   blink::WebPresentationController* controller_;
   presentation::PresentationServicePtr presentation_service_;
@@ -126,6 +128,8 @@ class CONTENT_EXPORT PresentationDispatcher
       std::set<blink::WebPresentationAvailabilityObserver*>;
   AvailabilityObserversSet availability_observers_;
 
+  bool listening_for_messages_;
+
   DISALLOW_COPY_AND_ASSIGN(PresentationDispatcher);
 };