Revert of Delete empty API files and cleaned up includes.

webrtc/api/objc/RTCVideoSource+Private.h

 /*
  *  Copyright 2015 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.
  */
 
 #import "RTCVideoSource.h"
 
-#include "webrtc/api/mediastreaminterface.h"
+#include "webrtc/api/videosourceinterface.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface RTCVideoSource ()
 
 /**
  * The VideoTrackSourceInterface object passed to this RTCVideoSource during
  * construction.
  */
 @property(nonatomic, readonly)
     rtc::scoped_refptr<webrtc::VideoTrackSourceInterface>
         nativeVideoSource;
 
 /** Initialize an RTCVideoSource from a native VideoTrackSourceInterface. */
 - (instancetype)initWithNativeVideoSource:
     (rtc::scoped_refptr<webrtc::VideoTrackSourceInterface>)nativeVideoSource
     NS_DESIGNATED_INITIALIZER;
 
 + (webrtc::MediaSourceInterface::SourceState)nativeSourceStateForState:
     (RTCSourceState)state;
 
 + (RTCSourceState)sourceStateForNativeState:
     (webrtc::MediaSourceInterface::SourceState)nativeState;
 
 + (NSString *)stringForState:(RTCSourceState)state;
 
 @end
 
 NS_ASSUME_NONNULL_END