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 182c5e2d77704b219f805806a7fca03f1e53443b..cae33fd6f2fb53b6951c1509bff4d912fd07040a 100644
--- a/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
+++ b/webrtc/sdk/android/src/jni/pc/mediastreamtrack_jni.cc
@@ -13,14 +13,6 @@
 
 namespace webrtc_jni {
 
-JNI_FUNCTION_DECLARATION(void,
-                         MediaStreamTrack_free,
-                         JNIEnv*,
-                         jclass,
-                         jlong j_p) {
-  reinterpret_cast<webrtc::MediaStreamTrackInterface*>(j_p)->Release();
-}
-
 JNI_FUNCTION_DECLARATION(jstring,
                          MediaStreamTrack_nativeId,
                          JNIEnv* jni,