[MediaSession] Add playbackState attribute to Blink MediaSession and use it to determine playback s…

content/browser/media/session/media_session_impl.h

Index: content/browser/media/session/media_session_impl.h
diff --git a/content/browser/media/session/media_session_impl.h b/content/browser/media/session/media_session_impl.h
index 148e3b236b3503826e7ad019943506f3671ae794..a34699ae2a7bb9f2a8893bb732f3688528da9478 100644
--- a/content/browser/media/session/media_session_impl.h
+++ b/content/browser/media/session/media_session_impl.h
@@ -176,6 +176,10 @@ class MediaSessionImpl : public MediaSession,
   // from this session.
   void OnServiceDestroyed(MediaSessionServiceImpl* service);
 
+  // Called when the playback state of a MediaSessionService has
+  // changed. Will notify observers of media session state change.
+  void OnMediaSessionPlaybackStateChanged(MediaSessionServiceImpl* service);
+
   // Called when the metadata of a MediaSessionService has changed. Will notify
   // observers if the service is currently routed.
   void OnMediaSessionMetadataChanged(MediaSessionServiceImpl* service);