Android: Add common function for adding/releasing native reference

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

Index: webrtc/sdk/android/api/org/webrtc/MediaStreamTrack.java
diff --git a/webrtc/sdk/android/api/org/webrtc/MediaStreamTrack.java b/webrtc/sdk/android/api/org/webrtc/MediaStreamTrack.java
index 95de37224513091b6cec48d15c4b352140a66267..656d02432599aef93888ef2b717740f591785402 100644
--- a/webrtc/sdk/android/api/org/webrtc/MediaStreamTrack.java
+++ b/webrtc/sdk/android/api/org/webrtc/MediaStreamTrack.java
@@ -47,7 +47,7 @@ public class MediaStreamTrack {
   }
 
   public void dispose() {
-    free(nativeTrack);
+    JniCommon.nativeReleaseRef(nativeTrack);
   }
 
   private static native String nativeId(long nativeTrack);
@@ -59,6 +59,4 @@ public class MediaStreamTrack {
   private static native boolean nativeSetEnabled(long nativeTrack, boolean enabled);
 
   private static native State nativeState(long nativeTrack);
-
-  private static native void free(long nativeTrack);
 }