Created a java wrapper for the callback OnAddTrack to PeerConnection.Observer

webrtc/api/android/java/src/org/webrtc/PeerConnection.java

Index: webrtc/api/android/java/src/org/webrtc/PeerConnection.java
diff --git a/webrtc/api/android/java/src/org/webrtc/PeerConnection.java b/webrtc/api/android/java/src/org/webrtc/PeerConnection.java
index 359b52ead7c93d46dec05b38c9d5efbb01909bd9..b24b2f9ebc6f9f0948ca5b8565a846b063747166 100644
--- a/webrtc/api/android/java/src/org/webrtc/PeerConnection.java
+++ b/webrtc/api/android/java/src/org/webrtc/PeerConnection.java
@@ -80,6 +80,9 @@ public class PeerConnection {
 
     /** Triggered when renegotiation is necessary. */
     public void onRenegotiationNeeded();
+
+    /** Triggered when a track is added to streams. */

[Taylor Brandstetter, 2016/11/17 23:02:53]

nit: I think a more descriptive comment would be "Triggered when a new track is
signaled by the remote peer, as a result of setRemoteDescription." Or something
similar.

[Zhi Huang, 2016/11/18 02:22:10]

Done.

+    public void onAddTrack(RtpReceiver receiver, MediaStream[] mediaStreams);
   }
 
   /** Java version of PeerConnectionInterface.IceServer. */