Android: Add common function for adding/releasing native reference

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

 /*
  *  Copyright 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 387 matching lines @@
     }
     localStreams.clear();
     for (RtpSender sender : senders) {
       sender.dispose();
     }
     senders.clear();
     for (RtpReceiver receiver : receivers) {
       receiver.dispose();
     }
     receivers.clear();
-    freePeerConnection(nativePeerConnection);
+    JniCommon.nativeReleaseRef(nativePeerConnection);
     freeObserver(nativeObserver);
   }
 
-  private static native void freePeerConnection(long nativePeerConnection);
-
   private static native void freeObserver(long nativeObserver);
 
   public native boolean nativeSetConfiguration(RTCConfiguration config, long nativeObserver);
 
   private native boolean nativeAddIceCandidate(
       String sdpMid, int sdpMLineIndex, String iceCandidateSdp);
 
   private native boolean nativeRemoveIceCandidates(final IceCandidate[] candidates);
 
   private native boolean nativeAddLocalStream(long nativeStream);
 
   private native void nativeRemoveLocalStream(long nativeStream);
 
   private native boolean nativeOldGetStats(StatsObserver observer, long nativeTrack);
 
   private native void nativeNewGetStats(RTCStatsCollectorCallback callback);
 
   private native RtpSender nativeCreateSender(String kind, String stream_id);
 
   private native List<RtpSender> nativeGetSenders();
 
   private native List<RtpReceiver> nativeGetReceivers();
 
   private native boolean nativeStartRtcEventLog(int file_descriptor, int max_size_bytes);
 
   private native void nativeStopRtcEventLog();
 }