Android: Add common function for adding/releasing native reference

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

Index: webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
diff --git a/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc b/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
index 849cdbbfb47e588419e542a10a27b74de3e5fef7..b92da39fc373eadc4373c541aa88bdac4a1c0673 100644
--- a/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
+++ b/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
@@ -13,10 +13,6 @@
 
 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());