Android: Add common function for adding/releasing native reference

webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc

 /*
  *  Copyright 2017 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.
  */
 
 #include "webrtc/api/mediastreaminterface.h"
 #include "webrtc/sdk/android/src/jni/jni_helpers.h"
 
 namespace webrtc_jni {
 
-JOW(void, MediaStreamTrack_free)(JNIEnv*, jclass, jlong j_p) {
-  reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->Release();
-}
-
 JOW(jstring, MediaStreamTrack_nativeId)(JNIEnv* jni, jclass, jlong j_p) {
   return JavaStringFromStdString(
       jni, reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->id());
 }
 
 JOW(jstring, MediaStreamTrack_nativeKind)(JNIEnv* jni, jclass, jlong j_p) {
   return JavaStringFromStdString(
       jni, reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->kind());
 }
 
 JOW(jboolean, MediaStreamTrack_nativeEnabled)(JNIEnv* jni, jclass, jlong j_p) {
   return reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->enabled();
 }
 
 JOW(jobject, MediaStreamTrack_nativeState)(JNIEnv* jni, jclass, jlong j_p) {
   return JavaEnumFromIndexAndClassName(
       jni, "MediaStreamTrack$State",
       reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->state());
 }
 
 JOW(jboolean, MediaStreamTrack_nativeSetEnabled)
 (JNIEnv* jni, jclass, jlong j_p, jboolean enabled) {
   return reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->set_enabled(
       enabled);
 }
 
 }  // namespace webrtc_jni