Allow MediaSession in iframes to be routed

content/browser/media/session/media_session_controller.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_CONTROLLER_H_
 #define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_CONTROLLER_H_
 
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "content/browser/media/session/media_session_player_observer.h"
@@ skipping 33 matching lines @@
 
   // Must be called when a pause occurs on the renderer side media player; keeps
   // the MediaSession instance in sync with renderer side behavior.
   void OnPlaybackPaused();
 
   // MediaSessionObserver implementation.
   void OnSuspend(int player_id) override;
   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_; }
 
  private:
   const WebContentsObserver::MediaPlayerId id_;
 
   // Non-owned pointer; |media_web_contents_observer_| is the owner of |this|.
   MediaWebContentsObserver* const media_web_contents_observer_;
 
   // Non-owned pointer; lifetime is the same as |media_web_contents_observer_|.
   MediaSessionImpl* const media_session_;
 
   int player_id_ = 0;
   bool has_session_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(MediaSessionController);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_CONTROLLER_H_