Compile rtc_api_objc on Mac.

webrtc/api/objc/RTCMediaStream.mm

 /*
  *  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 "RTCMediaStream.h"
 
 #include <vector>
 
 #import "webrtc/api/objc/RTCAudioTrack+Private.h"
 #import "webrtc/api/objc/RTCMediaStream+Private.h"
 #import "webrtc/api/objc/RTCMediaStreamTrack+Private.h"
 #import "webrtc/api/objc/RTCVideoTrack+Private.h"
 #import "webrtc/base/objc/NSString+StdString.h"
 
 @implementation RTCMediaStream {
   NSMutableArray *_audioTracks;
   NSMutableArray *_videoTracks;
   rtc::scoped_refptr<webrtc::MediaStreamInterface> _nativeMediaStream;
 }
 
-- (NSArray<RTCAudioTrack *> *)audioTracks {
+- (NSArray/*<RTCAudioTrack *>*/ *)audioTracks {
   return [_audioTracks copy];
 }
 
-- (NSArray<RTCVideoTrack *> *)videoTracks {
+- (NSArray/*<RTCVideoTrack *>*/ *)videoTracks {
   return [_videoTracks copy];
 }
 
 - (NSString *)streamId {
   return [NSString stringForStdString:_nativeMediaStream->label()];
 }
 
 - (void)addAudioTrack:(RTCAudioTrack *)audioTrack {
   if (_nativeMediaStream->AddTrack(audioTrack.nativeAudioTrack)) {
     [_audioTracks addObject:audioTrack];
@@ skipping 61 matching lines @@
       RTCMediaStreamTrackType type = RTCMediaStreamTrackTypeVideo;
       RTCVideoTrack *videoTrack =
           [[RTCVideoTrack alloc] initWithNativeTrack:track type:type];
       [_videoTracks addObject:videoTrack];
     }
   }
   return self;
 }
 
 @end