[Presentation API] Change ListenForSessionMessages API to client-style.

chrome/browser/media/router/media_router_mojo_impl.h

Index: chrome/browser/media/router/media_router_mojo_impl.h
diff --git a/chrome/browser/media/router/media_router_mojo_impl.h b/chrome/browser/media/router/media_router_mojo_impl.h
index 167b8e37c0cdffd9264c8f2db1a135b80282ea44..9fe0bdf44fdff2b6427fc576b56abbc8b6fb80a3 100644
--- a/chrome/browser/media/router/media_router_mojo_impl.h
+++ b/chrome/browser/media/router/media_router_mojo_impl.h
@@ -72,16 +72,7 @@ class MediaRouterMojoImpl : public MediaRouter,
   void SendRouteMessage(const MediaRoute::Id& route_id,
                         const std::string& message,
                         const SendRouteMessageCallback& callback) override;
-  void ListenForRouteMessages(
-      const std::vector<MediaRoute::Id>& route_ids,
-      const PresentationSessionMessageCallback& message_cb) override;
   void ClearIssue(const Issue::Id& issue_id) override;
-  void RegisterMediaSinksObserver(MediaSinksObserver* observer) override;
-  void UnregisterMediaSinksObserver(MediaSinksObserver* observer) override;
-  void RegisterMediaRoutesObserver(MediaRoutesObserver* observer) override;
-  void UnregisterMediaRoutesObserver(MediaRoutesObserver* observer) override;
-  void RegisterIssuesObserver(IssuesObserver* observer) override;
-  void UnregisterIssuesObserver(IssuesObserver* observer) override;
 
   const std::string& media_route_provider_extension_id() const {
     return media_route_provider_extension_id_;
@@ -95,6 +86,10 @@ class MediaRouterMojoImpl : public MediaRouter,
   friend class MediaRouterFactory;
   friend class MediaRouterMojoTest;
 
+  FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoImplTest,
+                           RegisterAndUnregisterMediaSinksObserver);
+  FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoImplTest,
+                           RegisterAndUnregisterMediaRoutesObserver);
   FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoExtensionTest,
                            DeferredBindingAndSuspension);
 
@@ -120,6 +115,18 @@ class MediaRouterMojoImpl : public MediaRouter,
   // Dispatches the Mojo requests queued in |pending_requests_|.
   void ExecutePendingRequests();
 
+  // MediaRouter implementation.
+  void RegisterMediaSinksObserver(MediaSinksObserver* observer) override;
+  void UnregisterMediaSinksObserver(MediaSinksObserver* observer) override;
+  void RegisterMediaRoutesObserver(MediaRoutesObserver* observer) override;
+  void UnregisterMediaRoutesObserver(MediaRoutesObserver* observer) override;
+  void RegisterIssuesObserver(IssuesObserver* observer) override;
+  void UnregisterIssuesObserver(IssuesObserver* observer) override;
+  void RegisterPresentationSessionMessagesObserver(
+      PresentationSessionMessagesObserver* observer) override;
+  void UnregisterPresentationSessionMessagesObserver(
+      PresentationSessionMessagesObserver* observer) override;
+
   // These calls invoke methods in the component extension via Mojo.
   void DoCreateRoute(const MediaSource::Id& source_id,
                      const MediaSink::Id& sink_id,
@@ -135,9 +142,7 @@ class MediaRouterMojoImpl : public MediaRouter,
   void DoSendSessionMessage(const MediaRoute::Id& route_id,
                             const std::string& message,
                             const SendRouteMessageCallback& callback);
-  void DoListenForRouteMessages(
-      const std::vector<MediaRoute::Id>& route_ids,
-      const PresentationSessionMessageCallback& message_cb);
+  void DoListenForRouteMessages(const MediaRoute::Id& route_id);
   void DoClearIssue(const Issue::Id& issue_id);
   void DoStartObservingMediaSinks(const MediaSource::Id& source_id);
   void DoStopObservingMediaSinks(const MediaSource::Id& source_id);
@@ -147,10 +152,10 @@ class MediaRouterMojoImpl : public MediaRouter,
   void DoStopObservingIssues();
 
   // Invoked when the next batch of messages arrives.
+  // |route_id|: ID of route of the messages.
   // |messages|: A list of messages received.
-  // |message_cb|: The callback to invoke to pass on the messages received.
-  void OnRouteMessageReceived(
-      const PresentationSessionMessageCallback& message_cb,
+  void OnRouteMessagesReceived(
+      const MediaRoute::Id& route_id,
       mojo::Array<interfaces::RouteMessagePtr> messages);
 
   // Error handler callback for |binding_| and |media_route_provider_|.
@@ -176,6 +181,16 @@ class MediaRouterMojoImpl : public MediaRouter,
 
   base::ObserverList<MediaRoutesObserver> routes_observers_;
 
+  base::ScopedPtrHashMap<
+      MediaRoute::Id,
+      scoped_ptr<base::ObserverList<PresentationSessionMessagesObserver>>>
+      messages_observers_;
+  // IDs of MediaRoutes being listened for messages. Note that this is
+  // different from |message_observers_| because we might be waiting for
+  // |OnRouteMessagesReceived()| to be invoked after all observers for that

[haibinlu, 2015/07/30 23:59:11]

if all observers for the route message have been removed, we should stop listen
for messages of this route. Without observers, sending messages from extension
to MR is bad. Shall we add a StopListenForMessage method too? 

[imcheng, 2015/08/03 18:56:33]

Currently we stop listening when we see there are no more observers when
messages from the extension arrive. It would be ideal to introduce a
StopListenForMessage so it would work better in the corner cases. Shall we do
this in a future patch after the extension side of StopListenForMessage is
implemented?

+  // route have been removed.
+  base::hash_set<MediaRoute::Id> listening_messages_for_routes_;
+
   // Binds |this| to a Mojo connection stub for interfaces::MediaRouter.
   scoped_ptr<mojo::Binding<interfaces::MediaRouter>> binding_;