Allow MediaSession in iframes to be routed

content/browser/media/session/media_session_controller.h

Index: content/browser/media/session/media_session_controller.h
diff --git a/content/browser/media/session/media_session_controller.h b/content/browser/media/session/media_session_controller.h
index f709828bd2b41f52e46511882cad666d71411951..e812d718442c11be3f1ca479b149649d3d2a8a3c 100644
--- a/content/browser/media/session/media_session_controller.h
+++ b/content/browser/media/session/media_session_controller.h
@@ -51,6 +51,10 @@ class CONTENT_EXPORT MediaSessionController
   void OnResume(int player_id) override;
   void OnSetVolumeMultiplier(int player_id, double volume_multiplier) override;
 
+  // Returns the WebContents-oriented media player id (RenderFrameHost and the
+  // frame-wise id).
+  const WebContentsObserver::MediaPlayerId& id() { return id_; };

[whywhat, 2016/11/28 19:59:14]

nit: give it a more descriptive name, it's confusing that the type is
MediaPlayerId but it's not the same as the player_id_ and player_id passed to
the methods above?

[Zhiqiang Zhang (Slow), 2016/11/30 16:40:59]

Done.

+
   // Test helpers.
   int get_player_id_for_testing() const { return player_id_; }