Add the OnAddTrack callback for Objective-C wrapper.

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
index de7608c3b9941dd1acffc6b8e8dc0d5c52211379..8e69ec6a649710622df7ddf892e026a6c6d5c7d3 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
@@ -127,9 +127,8 @@ void PeerConnectionDelegateAdapter::OnSignalingChange(
 
 void PeerConnectionDelegateAdapter::OnAddStream(
     rtc::scoped_refptr<MediaStreamInterface> stream) {
-  RTCMediaStream *mediaStream =
-      [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
   RTCPeerConnection *peer_connection = peer_connection_;
+  RTCMediaStream *mediaStream = [peer_connection mediaStreamForNativeStream:stream];
   [peer_connection.delegate peerConnection:peer_connection
                               didAddStream:mediaStream];
 }
@@ -141,6 +140,7 @@ void PeerConnectionDelegateAdapter::OnRemoveStream(
   RTCPeerConnection *peer_connection = peer_connection_;
   [peer_connection.delegate peerConnection:peer_connection
                            didRemoveStream:mediaStream];
+  [peer_connection removeNativeMediaStream:stream];
 }
 
 void PeerConnectionDelegateAdapter::OnDataChannel(
@@ -200,6 +200,28 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
                     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 =
+        [peer_connection mediaStreamForNativeStream: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
 
 
@@ -209,6 +231,7 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
   rtc::scoped_refptr<webrtc::PeerConnectionInterface> _peerConnection;
   std::unique_ptr<webrtc::MediaConstraints> _nativeConstraints;
   BOOL _hasStartedRtcEventLog;
+  NSMutableDictionary<NSString *, RTCMediaStream *> *_mediaStreamsByStreamId;
 }
 
 @synthesize delegate = _delegate;
@@ -238,6 +261,7 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
     }
     _localStreams = [[NSMutableArray alloc] init];
     _delegate = delegate;
+    _mediaStreamsByStreamId = [NSMutableDictionary dictionary];
   }
   return self;
 }
@@ -588,6 +612,21 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
   }
 }
 
+- (RTCMediaStream *)mediaStreamForNativeStream:
+    (rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream {
+  RTCMediaStream *mediaStream = _mediaStreamsByStreamId[@(stream->label().c_str())];

[tkchin_webrtc, 2017/02/23 19:23:36]

might need to use NSStringFromStdString

unless the string is guaranteed here to behave nicely

+  if (!mediaStream) {
+    mediaStream =
+        [[RTCMediaStream alloc] initWithNativeMediaStream:stream.get()];
+    _mediaStreamsByStreamId[@(stream->label().c_str())] = mediaStream;
+  }
+  return mediaStream;
+}
+
+- (void)removeNativeMediaStream:(rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream {
+  [_mediaStreamsByStreamId removeObjectForKey:@(stream->label().c_str())];
+}
+
 - (rtc::scoped_refptr<webrtc::PeerConnectionInterface>)nativePeerConnection {
   return _peerConnection;
 }