[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 2dbf07c3f1387b0d1b7f34bf4c3d39a4221eda57..aa5d03c5cdc896a209aecba65cafa7d237e15534 100644
--- a/content/renderer/presentation/presentation_dispatcher.h
+++ b/content/renderer/presentation/presentation_dispatcher.h
@@ -93,6 +93,8 @@ 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_;
@@ -121,6 +123,8 @@ class CONTENT_EXPORT PresentationDispatcher
       std::set<blink::WebPresentationAvailabilityObserver*>;
   AvailabilityObserversSet availability_observers_;
 
+  bool listening_for_messages_;
+
   DISALLOW_COPY_AND_ASSIGN(PresentationDispatcher);
 };