Reland of Split iOS sdk in to separate targets

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCVideoCapturer.m

 /*
  *  Copyright 2017 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 "WebRTC/RTCVideoCapturer.h"
 
 @implementation RTCVideoCapturer
 
 @synthesize delegate = _delegate;
 
 - (instancetype)initWithDelegate:(id<RTCVideoCapturerDelegate>)delegate {
   NSAssert(delegate != nil, @"delegate cannot be nil");
   if (self = [super init]) {
     _delegate = delegate;
   }
   return self;
 }
 
 @end