Android: Add common function for adding/releasing native reference

webrtc/sdk/android/api/org/webrtc/PeerConnection.java

Index: webrtc/sdk/android/api/org/webrtc/PeerConnection.java
diff --git a/webrtc/sdk/android/api/org/webrtc/PeerConnection.java b/webrtc/sdk/android/api/org/webrtc/PeerConnection.java
index b2155c42e4d0e79561adb746a3ac67a989fbc179..88610a43c0c973aeab84ab13246634efd757ad02 100644
--- a/webrtc/sdk/android/api/org/webrtc/PeerConnection.java
+++ b/webrtc/sdk/android/api/org/webrtc/PeerConnection.java
@@ -405,12 +405,10 @@ public class PeerConnection {
       receiver.dispose();
     }
     receivers.clear();
-    freePeerConnection(nativePeerConnection);
+    JniCommon.nativeReleaseRef(nativePeerConnection);
     freeObserver(nativeObserver);
   }
 
-  private static native void freePeerConnection(long nativePeerConnection);
-
   private static native void freeObserver(long nativeObserver);
 
   public native boolean nativeSetConfiguration(RTCConfiguration config, long nativeObserver);