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 109 matching lines @@
     PeerConnectionInterface::SignalingState new_state) {
   RTCSignalingState state =
       [[RTCPeerConnection class] signalingStateForNativeState:new_state];
   RTCPeerConnection *peer_connection = peer_connection_;
   [peer_connection.delegate peerConnection:peer_connection
                    didChangeSignalingState:state];
 }
 
 void PeerConnectionDelegateAdapter::OnAddStream(
     rtc::scoped_refptr<MediaStreamInterface> stream) {
-  RTCMediaStream *mediaStream =
-      [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
+  RTCMediaStream* mediaStream = GetOrCreateObjcStream(stream);
   RTCPeerConnection *peer_connection = peer_connection_;
   [peer_connection.delegate peerConnection:peer_connection
                               didAddStream:mediaStream];
 }
 
 void PeerConnectionDelegateAdapter::OnRemoveStream(
     rtc::scoped_refptr<MediaStreamInterface> stream) {
   RTCMediaStream *mediaStream =
       [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
   RTCPeerConnection *peer_connection = peer_connection_;
@@ skipping 51 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,
+    std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams) {
+  RTCRtpReceiver* rtpReceiver =

[tkchin_webrtc, 2016/11/22 20:41:34]

* on right
RTCRtpReceiver *rtpReceiver

here and elsewhere

[Zhi Huang, 2016/11/22 23:38:42]

Done.

+      [[RTCRtpReceiver alloc] initWithNativeRtpReceiver:receiver];
+  NSMutableArray* mediaStreams =
+      [NSMutableArray arrayWithCapacity:streams.size()];
+  for (const auto stream : streams) {
+    RTCMediaStream* mediaStream = GetOrCreateObjcStream(stream);
+    [mediaStreams addObject:mediaStream];
+  }
+  RTCPeerConnection* peer_connection = peer_connection_;
+  [peer_connection.delegate peerConnection:peer_connection
+                               didAddTrack:rtpReceiver
+                           attachedStreams:mediaStreams];
+}
+
+RTCMediaStream* PeerConnectionDelegateAdapter::GetOrCreateObjcStream(

[tkchin_webrtc, 2016/11/22 20:41:34]

I'd suggest placing these streams refs on peerconnection instead so that their
lifetime is tied to the peerconnection. You can add private methods for this.

Currently, if the delegate outlives the peerconnection, these streams in the
dictionary won't get deallocated.

[Zhi Huang, 2016/11/22 23:38:42]

Ah, yes. This is a good point.

Done.

+    rtc::scoped_refptr<MediaStreamInterface> stream) {
+  RTCMediaStream* mediaStream =
+      nativeToObjcMediaStream_[[NSNumber numberWithLong:(long)stream.get()]];
+  if (!mediaStream) {
+    mediaStream =
+        [[RTCMediaStream alloc] initWithNativeMediaStream:stream.get()];
+    nativeToObjcMediaStream_[[NSNumber numberWithLong:(long)stream.get()]] =
+        mediaStream;
+  }
+  return mediaStream;
+}
+
 }  // namespace webrtc
 
 
 @implementation RTCPeerConnection {
   NSMutableArray<RTCMediaStream *> *_localStreams;
   std::unique_ptr<webrtc::PeerConnectionDelegateAdapter> _observer;
   rtc::scoped_refptr<webrtc::PeerConnectionInterface> _peerConnection;
   BOOL _hasStartedRtcEventLog;
 }
 
@@ skipping 370 matching lines @@
     case RTCStatsOutputLevelDebug:
       return webrtc::PeerConnectionInterface::kStatsOutputLevelDebug;
   }
 }
 
 - (rtc::scoped_refptr<webrtc::PeerConnectionInterface>)nativePeerConnection {
   return _peerConnection;
 }
 
 @end