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

webrtc/api/videosourceproxy.h

 /*
  *  Copyright 2012 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.
  */
 
 #ifndef WEBRTC_API_VIDEOSOURCEPROXY_H_
 #define WEBRTC_API_VIDEOSOURCEPROXY_H_
 
 #include "webrtc/api/proxy.h"
 #include "webrtc/api/mediastreaminterface.h"
 
 namespace webrtc {
 
-// VideoTrackSourceInterface makes sure the real VideoTrackSourceInterface
-// implementation is
-// destroyed on the signaling thread and marshals all method calls to the
-// signaling thread.
+// Makes sure the real VideoTrackSourceInterface implementation is destroyed on
+// the signaling thread and marshals all method calls to the signaling thread.
+// TODO(deadbeef): Move this to .cc file and out of api/. What threads methods
+// are called on is an implementation detail.
 BEGIN_PROXY_MAP(VideoTrackSource)
   PROXY_SIGNALING_THREAD_DESTRUCTOR()
   PROXY_CONSTMETHOD0(SourceState, state)
   PROXY_CONSTMETHOD0(bool, remote)
   PROXY_CONSTMETHOD0(bool, is_screencast)
   PROXY_CONSTMETHOD0(rtc::Optional<bool>, needs_denoising)
   PROXY_METHOD1(bool, GetStats, Stats*)
   PROXY_WORKER_METHOD2(void,
                        AddOrUpdateSink,
                        rtc::VideoSinkInterface<VideoFrame>*,
                        const rtc::VideoSinkWants&)
   PROXY_WORKER_METHOD1(void, RemoveSink, rtc::VideoSinkInterface<VideoFrame>*)
   PROXY_METHOD1(void, RegisterObserver, ObserverInterface*)
   PROXY_METHOD1(void, UnregisterObserver, ObserverInterface*)
 END_PROXY_MAP()
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_VIDEOSOURCEPROXY_H_