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 b4a873847de5bda226a1c72d23a48b7eff97f1bb..cdc8c42aeca3354a4fd74f6ab27338f2494e1956 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm
@@ -127,8 +127,7 @@ void PeerConnectionDelegateAdapter::OnSignalingChange(
 
 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];
@@ -200,6 +199,36 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
                     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