Android: Add common function for adding/releasing native reference

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

 /*
  *  Copyright 2015 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 64 matching lines @@
     return dtmfSender;
   }
 
   public void dispose() {
     if (dtmfSender != null) {
       dtmfSender.dispose();
     }
     if (cachedTrack != null && ownsTrack) {
       cachedTrack.dispose();
     }
-    free(nativeRtpSender);
+    JniCommon.nativeReleaseRef(nativeRtpSender);
   }
 
   private static native boolean nativeSetTrack(long nativeRtpSender, long nativeTrack);
 
   // This should increment the reference count of the track.
   // Will be released in dispose() or setTrack().
   private static native long nativeGetTrack(long nativeRtpSender);
 
   // This should increment the reference count of the DTMF sender.
   // Will be released in dispose().
   private static native long nativeGetDtmfSender(long nativeRtpSender);
 
   private static native boolean nativeSetParameters(long nativeRtpSender, RtpParameters parameters);
 
   private static native RtpParameters nativeGetParameters(long nativeRtpSender);
 
   private static native String nativeId(long nativeRtpSender);
-
-  private static native void free(long nativeRtpSender);
 };