Adding more comments to every header file in api/ subdirectory.

webrtc/api/mediastreamtrackproxy.h

 /*
  *  Copyright 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 // This file includes proxy classes for tracks. The purpose is
 // to make sure tracks are only accessed from the signaling thread.
 
 #ifndef WEBRTC_API_MEDIASTREAMTRACKPROXY_H_
 #define WEBRTC_API_MEDIASTREAMTRACKPROXY_H_
 
 #include <string>
 
 #include "webrtc/api/mediastreaminterface.h"
 #include "webrtc/api/proxy.h"
 
 namespace webrtc {
 
+// TODO(deadbeef): Move this to .cc file and out of api/. What threads methods
+// are called on is an implementation detail.
+
 BEGIN_SIGNALING_PROXY_MAP(AudioTrack)
   PROXY_SIGNALING_THREAD_DESTRUCTOR()
   PROXY_CONSTMETHOD0(std::string, kind)
   PROXY_CONSTMETHOD0(std::string, id)
   PROXY_CONSTMETHOD0(TrackState, state)
   PROXY_CONSTMETHOD0(bool, enabled)
   PROXY_CONSTMETHOD0(AudioSourceInterface*, GetSource)
   PROXY_METHOD1(void, AddSink, AudioTrackSinkInterface*)
   PROXY_METHOD1(void, RemoveSink, AudioTrackSinkInterface*)
   PROXY_METHOD1(bool, GetSignalLevel, int*)
@@ skipping 19 matching lines @@
   PROXY_WORKER_METHOD1(void, RemoveSink, rtc::VideoSinkInterface<VideoFrame>*)
   PROXY_CONSTMETHOD0(VideoTrackSourceInterface*, GetSource)
 
   PROXY_METHOD1(void, RegisterObserver, ObserverInterface*)
   PROXY_METHOD1(void, UnregisterObserver, ObserverInterface*)
 END_PROXY_MAP()
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_MEDIASTREAMTRACKPROXY_H_