Support for unmixed remote audio into tracks.

BUG=chromium:121673
R=solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/1505253004 .

Cr-Commit-Position: refs/heads/master@{#10995}
diff --git a/talk/app/webrtc/mediastreaminterface.h b/talk/app/webrtc/mediastreaminterface.h
index 00782cb..5327bd2 100644
--- a/talk/app/webrtc/mediastreaminterface.h
+++ b/talk/app/webrtc/mediastreaminterface.h
@@ -167,6 +167,8 @@
   // TODO(xians): Makes all the interface pure virtual after Chrome has their
   // implementations.
   // Sets the volume to the source. |volume| is in  the range of [0, 10].
+  // TODO(tommi): This method should be on the track and ideally volume should
+  // be applied in the track in a way that does not affect clones of the track.
   virtual void SetVolume(double volume) {}
 
   // Registers/unregisters observer to the audio source.