Android: Add common function for adding/releasing native reference

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

Index: webrtc/sdk/android/src/jni/pc/mediasource_jni.cc
diff --git a/webrtc/sdk/android/src/jni/pc/mediasource_jni.cc b/webrtc/sdk/android/src/jni/pc/mediasource_jni.cc
index 1fc46b3c2fc2678acf8aa7cf8c16236fc005f877..3115d307b8fb1740a14205b57f86af3830b6b918 100644
--- a/webrtc/sdk/android/src/jni/pc/mediasource_jni.cc
+++ b/webrtc/sdk/android/src/jni/pc/mediasource_jni.cc
@@ -13,10 +13,6 @@
 
 namespace webrtc_jni {
 
-JOW(void, MediaSource_free)(JNIEnv*, jclass, jlong j_p) {
-  reinterpret_cast<rtc::RefCountInterface*>(j_p)->Release();
-}
-
 JOW(jobject, MediaSource_nativeState)(JNIEnv* jni, jclass, jlong j_p) {
   rtc::scoped_refptr<webrtc::MediaSourceInterface> p(
       reinterpret_cast<webrtc::MediaSourceInterface*>(j_p));