Implement MediaSession on top of the WebMediaPlayerDelegate.

content/renderer/media/android/renderer_media_player_manager.h

Index: content/renderer/media/android/renderer_media_player_manager.h
diff --git a/content/renderer/media/android/renderer_media_player_manager.h b/content/renderer/media/android/renderer_media_player_manager.h
index b4eb44be7c93b3b00854b0874ef141cf2c052d6f..1e790596bc06e29c231b8549a7c2466304b2a438 100644
--- a/content/renderer/media/android/renderer_media_player_manager.h
+++ b/content/renderer/media/android/renderer_media_player_manager.h
@@ -49,7 +49,8 @@ class RendererMediaPlayerManager :
                   const GURL& first_party_for_cookies,
                   int demuxer_client_id,
                   const GURL& frame_url,
-                  bool allow_credentials) override;
+                  bool allow_credentials,
+                  media::WebMediaPlayerDelegate::Observer* observer) override;
 
   // Starts the player.
   void Start(int player_id) override;