Add empty placeholder files for remote audio tracks.

talk/app/webrtc/remoteaudiotrack.h

Index: talk/app/webrtc/remoteaudiotrack.h
diff --git a/talk/session/media/voicechannel.h b/talk/app/webrtc/remoteaudiotrack.h
similarity index 89%
copy from talk/session/media/voicechannel.h
copy to talk/app/webrtc/remoteaudiotrack.h
index 6c1b6afdd55aab2df3325297afe0efde2b76b727..4ce4e792763e79a5f9f84fb98011054277375ae9 100644
--- a/talk/session/media/voicechannel.h
+++ b/talk/app/webrtc/remoteaudiotrack.h
@@ -1,6 +1,6 @@
 /*
  * libjingle
- * Copyright 2004 Google Inc.
+ * Copyright 2015 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -25,9 +25,7 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _VOICECHANNEL_H_
-#define _VOICECHANNEL_H_
+#ifndef TALK_APP_WEBRTC_REMOTEAUDIOTRACK_H_
+#define TALK_APP_WEBRTC_REMOTEAUDIOTRACK_H_
 
-#include "talk/session/media/channel.h"
-
-#endif // _VOICECHANNEL_H_
+#endif  // TALK_APP_WEBRTC_REMOTEAUDIOTRACK_H_