Implement one-shot audio focus inside MediaSession

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 2a6d027f5e4222e12b06e93ea826f6b3d858600f..e8ee0a3d29dbac91d15435b94ac1152b743137e7 100644
--- a/content/browser/media/session/media_session_impl.h
+++ b/content/browser/media/session/media_session_impl.h
@@ -209,8 +209,8 @@ class MediaSessionImpl : public MediaSession,
   // delegate to abandon the audio focus.
   CONTENT_EXPORT void AbandonSystemAudioFocusIfNeeded();
 
-  // Notifies WebContents about the state change of the media session.
-  void UpdateWebContents();
+  // Notifies observers about the state change of the media session.
+  void DispatchStateChange();

[whywhat, 2016/11/03 14:32:17]

nit: you could call it NotifyObserversAboutStateChange or just
NotifyAboutStateChange or something to make the name match what's going on.
DispatchStateChange may sound like changing state of observers or something
else.

[Zhiqiang Zhang (Slow), 2016/11/04 14:10:54]

Done.

 
   // Internal method that should be used instead of setting audio_focus_state_.
   // It sets audio_focus_state_ and notifies observers about the state change.
@@ -231,9 +231,13 @@ class MediaSessionImpl : public MediaSession,
   CONTENT_EXPORT bool AddPepperPlayer(MediaSessionPlayerObserver* observer,
                                       int player_id);
 
+  CONTENT_EXPORT bool AddOneShotPlayer(MediaSessionPlayerObserver* observer,
+                                       int player_id);
+
   std::unique_ptr<AudioFocusDelegate> delegate_;
   PlayersMap players_;

[whywhat, 2016/11/03 14:32:17]

nit: perhaps we should rename players_ into normal_players_ and have
AddNormalPlayer or something to highlight that pepper_players_ and
one_shot_players_ are not players_.

[Zhiqiang Zhang (Slow), 2016/11/04 14:10:54]

Done.

   PlayersMap pepper_players_;
+  PlayersMap one_shot_players_;
 
   State audio_focus_state_;
   MediaSession::SuspendType suspend_type_;