Adding "first packet received" notification to PeerConnectionObserver.

talk/app/webrtc/objc/RTCPeerConnectionObserver.mm

 /*
  * libjingle
  * Copyright 2013 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 87 matching lines @@
 }
 
 void RTCPeerConnectionObserver::OnIceCandidate(
     const IceCandidateInterface* candidate) {
   RTCICECandidate* iceCandidate =
       [[RTCICECandidate alloc] initWithCandidate:candidate];
   [_peerConnection.delegate peerConnection:_peerConnection
                            gotICECandidate:iceCandidate];
 }
 
+void RTCPeerConnectionObserver::OnFirstMediaPacketReceived() {
+  id<RTCPeerConnectionDelegate> delegate = _peerConnection.delegate;
+  [delegate peerConnectionOnFirstMediaPacketReceived:_peerConnection];
+}
+
 }  // namespace webrtc