Media Remoting: Add mojo interfaces between browser and extension.

chrome/browser/media/router/media_router_base.h

Index: chrome/browser/media/router/media_router_base.h
diff --git a/chrome/browser/media/router/media_router_base.h b/chrome/browser/media/router/media_router_base.h
index c482662b671eb500db9b5d978ab1ab34a18d7fda..807ac26fd262cb0e3a31eebc02b408c7389b3759 100644
--- a/chrome/browser/media/router/media_router_base.h
+++ b/chrome/browser/media/router/media_router_base.h
@@ -37,6 +37,10 @@ class MediaRouterBase : public MediaRouter {
   scoped_refptr<MediaRouteController> GetRouteController(
       const MediaRoute::Id& route_id) override;
 
+  void RegisterRemotingSource(int32_t tab_id,
+                              CastRemotingConnector* remoting_source) override;
+  void UnregisterRemotingSource(int32_t tab_id) override;
+
  protected:
   FRIEND_TEST_ALL_PREFIXES(MediaRouterMojoImplTest,
                            PresentationConnectionStateChangedCallback);
@@ -73,6 +77,11 @@ class MediaRouterBase : public MediaRouter {
       std::unique_ptr<PresentationConnectionStateChangedCallbacks>>
       presentation_connection_state_callbacks_;
 
+  // Stores CastRemotingConnectors that can be connected to the MediaRemoter
+  // for media remoting when MediaRemoter is started. The map uses the tab ID
+  // as the key.
+  std::unordered_map<int32_t, CastRemotingConnector*> remoting_sources_;

[imcheng, 2017/07/05 18:53:08]

Consider using base::flat_map if the number of entries is expected to be small?
(< 3-4 entries)
https://cs.chromium.org/chromium/src/base/containers/README.md?type=cs

[xjz, 2017/07/06 22:03:45]

There will be one CastRemotingConnector for each webContent, so the number of
entries might be large. As discussed offline, keep using std::unordered_map.

+
  private:
   friend class MediaRouterBaseTest;
   friend class MediaRouterFactory;