Fix build due to merge of 7595842 and renaming due to 8eb87f0

I.e. rename mVideoCallback -> mCallback. Line with original name
was added in mwd, renaming was done in master. The renaming CL
was cherry-picked to mwd (and build probably fixed there).

Change-Id: I462a0fedd00293a148404e1419740bf492ae5de9

telecomm/java/android/telecom/VideoCallImpl.java

@@ -176,7 +176,7 @@ public class VideoCallImpl extends VideoCall {
 
     /** {@inheritDoc} */
     public void removeVideoCallListener() {
-        mVideoCallListener = null;
+        mCallback = null;
         try {
             mVideoProvider.removeVideoCallback(mBinder);
         } catch (RemoteException e) {