Make getNativePeerConnection public.

Bug: webrtc:8662
Change-Id: Id23b5e047a2c479bef1c4dd7985c3199c6310eb6
Reviewed-on: https://webrtc-review.googlesource.com/35720
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21547}

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

@@ -788,7 +788,7 @@ public class PeerConnection {
   }
 
   @CalledByNative
-  long getNativePeerConnection() {
+  public long getNativePeerConnection() {
     return nativePeerConnection;
   }