Android: Add common function for adding/releasing native reference

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

Index: webrtc/sdk/android/src/jni/pc/dtmfsender_jni.cc
diff --git a/webrtc/sdk/android/src/jni/pc/dtmfsender_jni.cc b/webrtc/sdk/android/src/jni/pc/dtmfsender_jni.cc
index b304956104329675d2ffdbed325caf56db52e597..fd1d195c08c3183dbb6631139a3106ef253a3f7c 100644
--- a/webrtc/sdk/android/src/jni/pc/dtmfsender_jni.cc
+++ b/webrtc/sdk/android/src/jni/pc/dtmfsender_jni.cc
@@ -62,13 +62,4 @@ JNI_FUNCTION_DECLARATION(jint,
       ->inter_tone_gap();
 }
 
-JNI_FUNCTION_DECLARATION(void,
-                         DtmfSender_free,
-                         JNIEnv* jni,
-                         jclass,
-                         jlong j_dtmf_sender_pointer) {
-  reinterpret_cast<webrtc::DtmfSenderInterface*>(j_dtmf_sender_pointer)
-      ->Release();
-}
-
 }  // namespace webrtc_jni