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..834af3c122ab9cfb01c912a217010c46882940ee 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 getOrCreateObjcStream: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 removeObjcStream:stream];
 }
 
 void PeerConnectionDelegateAdapter::OnDataChannel(
@@ -200,6 +200,25 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
                     didRemoveIceCandidates:ice_candidates];
 }
 
+void PeerConnectionDelegateAdapter::OnAddTrack(

[tkchin_webrtc, 2017/02/15 23:43:48]

strange that the method is OnAddTrack but it gives you a RtpReceiver
is this temporary or permanent? What's in the w3c spec?

[Taylor Brandstetter, 2017/02/16 01:07:06]

That's what's in the spec (it's called "ontrack" there). Yes, OnAddTrack gives
you an RtpReceiver, and RemoveTrack takes an RtpSender. Strange world we've come
to. :)

+    rtc::scoped_refptr<RtpReceiverInterface> receiver,
+    const std::vector<rtc::scoped_refptr<MediaStreamInterface>>& streams) {
+  RTCRtpReceiver *rtpReceiver =

[tkchin_webrtc, 2017/02/15 23:43:47]

use C++ style in C++ methods

[Zhi Huang, 2017/02/21 04:55:50]

Done.

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

[tkchin_webrtc, 2017/02/15 23:43:48]

ObjC naming usually follows type (so I'd expect
peerConnection:didAddRtpReceiver:streams:).
But if spec is that the method name is track but the type is rtpreceiver then
we'll do that. attachedStreams->streams though

[Zhi Huang, 2017/02/21 04:55:50]

Done.

+                           attachedStreams:mediaStreams];
+}
+
 }  // namespace webrtc
 
 
@@ -209,6 +228,7 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
   rtc::scoped_refptr<webrtc::PeerConnectionInterface> _peerConnection;
   std::unique_ptr<webrtc::MediaConstraints> _nativeConstraints;
   BOOL _hasStartedRtcEventLog;
+  NSMutableDictionary *_nativeToObjcMediaStream;

[tkchin_webrtc, 2017/02/15 23:43:48]

NSMutableDictionary<NSNumber, RTCMediaStream *> *_mediaStreamsByStreamId;

[Zhi Huang, 2017/02/21 04:55:50]

Done.

 }
 
 @synthesize delegate = _delegate;
@@ -238,6 +258,7 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
     }
     _localStreams = [[NSMutableArray alloc] init];
     _delegate = delegate;
+    _nativeToObjcMediaStream = [NSMutableDictionary dictionary];
   }
   return self;
 }
@@ -588,6 +609,23 @@ void PeerConnectionDelegateAdapter::OnIceCandidatesRemoved(
   }
 }
 
+- (RTCMediaStream *)getOrCreateObjcStream:

[tkchin_webrtc, 2017/02/15 23:43:48]

"get" prefix is forbidden in ObjC style

- (RTCMediaStream
*)mediaStreamForNativeStream:(rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream
{

}

[Zhi Huang, 2017/02/21 04:55:50]

Done.

+    (rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream {
+  RTCMediaStream *mediaStream =
+      _nativeToObjcMediaStream[[NSNumber numberWithLong:(long)stream.get()]];

[tkchin_webrtc, 2017/02/15 23:43:48]

Is there anything better than pointer value to use as a key here?

use @((long)stream.get());

[Taylor Brandstetter, 2017/02/16 01:07:06]

They have an ID field which should be unique within a PeerConnection at any
given time.

+  if (!mediaStream) {
+    mediaStream =
+        [[RTCMediaStream alloc] initWithNativeMediaStream:stream.get()];
+    _nativeToObjcMediaStream[[NSNumber numberWithLong:(long)stream.get()]] =
+        mediaStream;
+  }
+  return mediaStream;
+}
+
+- (void)removeObjcStream:(rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream {

[tkchin_webrtc, 2017/02/15 23:43:47]

nit:
-
(void)removeNativeMediaStream:(rtc::scoped_refptr<webrtc::MediaStreamInterface>)stream);

[Zhi Huang, 2017/02/21 04:55:50]

Done.

+  [_nativeToObjcMediaStream removeObjectForKey:[NSNumber numberWithLong:(long)stream.get()]];
+}
+
 - (rtc::scoped_refptr<webrtc::PeerConnectionInterface>)nativePeerConnection {
   return _peerConnection;
 }