diff --git a/api/media_stream_interface.h b/api/media_stream_interface.h
index d61dd98..7e01028 100644
--- a/api/media_stream_interface.h
+++ b/api/media_stream_interface.h
@@ -333,6 +333,8 @@
   virtual rtc::scoped_refptr<VideoTrackInterface> FindVideoTrack(
       const std::string& track_id) = 0;
 
+  // Takes ownership of added tracks.
+  // TODO(hta): Should take scoped_refptr rather than raw pointer.
   virtual bool AddTrack(AudioTrackInterface* track) = 0;
   virtual bool AddTrack(VideoTrackInterface* track) = 0;
   virtual bool RemoveTrack(AudioTrackInterface* track) = 0;