Added a callback function OnAddTrack to PeerConnectionObserver

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h

Index: webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h
index 60ab868a7c515a9dec6a54f7a4eafe008826cb29..dd911542d05a5257cbc9a8ed3bfe42da29b32fd5 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h
+++ b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnection+Private.h
@@ -49,6 +49,10 @@ class PeerConnectionDelegateAdapter : public PeerConnectionObserver {
   void OnIceCandidatesRemoved(
       const std::vector<cricket::Candidate>& candidates) override;
 
+  void OnAddTrack(
+        rtc::scoped_refptr<RtpReceiverInterface> receiver,
+        std::vector<rtc::scoped_refptr<MediaStreamInterface>> streams) override;
+
  private:
   __weak RTCPeerConnection *peer_connection_;
 };