[Media Router] Notify MRUI of a media status update when it starts observing

chrome/browser/media/router/mojo/media_route_controller.h

Index: chrome/browser/media/router/mojo/media_route_controller.h
diff --git a/chrome/browser/media/router/mojo/media_route_controller.h b/chrome/browser/media/router/mojo/media_route_controller.h
index 5a5fab0bc132e11c94d9715cc02d71e9f550a224..ff6e2dc3502a7f76a10ef7cb4242c3820cacb7c5 100644
--- a/chrome/browser/media/router/mojo/media_route_controller.h
+++ b/chrome/browser/media/router/mojo/media_route_controller.h
@@ -44,6 +44,10 @@ class MediaRouteController : public mojom::MediaStatusObserver,
     // Removes itself as an observer if |controller_| is still valid.
     virtual ~Observer();
 
+    // Notifies itself with the latest media status that the controller has
+    // received.
+    void CheckForMediaStatusUpdates();

[mark a. foltz, 2017/05/12 21:00:58]

Is this necessary?

[takumif, 2017/05/12 22:20:58]

Removed.

+
     virtual void OnMediaStatusUpdated(const MediaStatus& status) = 0;
 
     // Returns a reference to the observed MediaRouteController. The reference
@@ -105,6 +109,10 @@ class MediaRouteController : public mojom::MediaStatusObserver,
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
+  const base::Optional<MediaStatus>& current_media_status() const {
+    return current_media_status_;
+  }
+
   // Called when the connection between |this| and the MediaControllerPtr or
   // the MediaStatusObserver binding is no longer valid. Notifies
   // |media_router_| and |observers_| to dispose their references to |this|.
@@ -129,6 +137,9 @@ class MediaRouteController : public mojom::MediaStatusObserver,
   // This becomes false when the controller is invalidated.
   bool is_valid_ = true;
 
+  // The latest media status that the controller has been notified with.
+  base::Optional<MediaStatus> current_media_status_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaRouteController);
 };