Delete empty API files and cleaned up includes.

webrtc/api/videotracksource.h

 /*
  *  Copyright 2016 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_VIDEOTRACKSOURCE_H_
 #define WEBRTC_API_VIDEOTRACKSOURCE_H_
 
+#include "webrtc/api/mediastreaminterface.h"
 #include "webrtc/api/notifier.h"
-#include "webrtc/api/videosourceinterface.h"
 #include "webrtc/media/base/mediachannel.h"
 #include "webrtc/media/base/videosinkinterface.h"
 
 // VideoTrackSource implements VideoTrackSourceInterface.
 namespace webrtc {
 
 class VideoTrackSource : public Notifier<VideoTrackSourceInterface> {
  public:
   VideoTrackSource(rtc::VideoSourceInterface<cricket::VideoFrame>* source,
                    rtc::Thread* worker_thread,
@@ skipping 26 matching lines @@
   rtc::VideoSourceInterface<cricket::VideoFrame>* source_;
   rtc::Thread* worker_thread_;
   cricket::VideoOptions options_;
   SourceState state_;
   const bool remote_;
 };
 
 }  // namespace webrtc
 
 #endif  //  WEBRTC_API_VIDEOTRACKSOURCE_H_