Add the OnAddTrack callback for Objective-C wrapper.

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.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.
  */
 
@@ skipping 182 matching lines @@
         new JsepIceCandidate(candidate.transport_name(), -1, candidate));
     RTCIceCandidate* ice_candidate = [[RTCIceCandidate alloc]
         initWithNativeCandidate:candidate_wrapper.get()];
     [ice_candidates addObject:ice_candidate];
   }
   RTCPeerConnection* peer_connection = peer_connection_;
   [peer_connection.delegate peerConnection:peer_connection
                     didRemoveIceCandidates:ice_candidates];
 }
 
+void PeerConnectionDelegateAdapter::OnAddTrack(
+    rtc::scoped_refptr<RtpReceiverInterface> receiver,
+    const std::vector<rtc::scoped_refptr<MediaStreamInterface>>& streams) {
+  RTCRtpReceiver* rtpReceiver =
+      [[RTCRtpReceiver alloc] initWithNativeRtpReceiver:receiver];
+  NSMutableArray* mediaStreams =
+      [NSMutableArray arrayWithCapacity:streams.size()];
+
+  RTCPeerConnection* peer_connection = peer_connection_;
+  for (const auto stream : streams) {
+    RTCMediaStream *mediaStream =
+        [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
+    [mediaStreams addObject:mediaStream];
+  }
+  if ([peer_connection.delegate
+      respondsToSelector:@selector(peerConnection:didAddTrack:streams:)]) {
+    [peer_connection.delegate peerConnection:peer_connection
+                                 didAddTrack:rtpReceiver
+                                     streams:mediaStreams];
+  }
+}
+
 }  // namespace webrtc
 
 
 @implementation RTCPeerConnection {
   NSMutableArray<RTCMediaStream *> *_localStreams;
   std::unique_ptr<webrtc::PeerConnectionDelegateAdapter> _observer;
   rtc::scoped_refptr<webrtc::PeerConnectionInterface> _peerConnection;
   std::unique_ptr<webrtc::MediaConstraints> _nativeConstraints;
   BOOL _hasStartedRtcEventLog;
 }
@@ skipping 373 matching lines @@
     case RTCStatsOutputLevelDebug:
       return webrtc::PeerConnectionInterface::kStatsOutputLevelDebug;
   }
 }
 
 - (rtc::scoped_refptr<webrtc::PeerConnectionInterface>)nativePeerConnection {
   return _peerConnection;
 }
 
 @end