anchor.diff:      // <expiration time in seconds since the unix epoch> }.
       _fb.callMethod('auth', [
         token,
  -      (err, [result]) {
  -        if (err != null) {
  -          c.completeError(err);
  -        } else {
  -          c.complete(decodeAuthData(result));
  -        }
  -      },
  +      _getAuthCallback(c),
         (err) {
           c.completeError(err);
         }
  
positive.code:   Future authAnonymously({remember: 'default'}) {
      var c = new Completer();
      _fb.callMethod('authAnonymously', [
        (err, [result]) {
          if (err != null) {
            c.completeError(err);
          } else {
            c.complete(decodeAuthData(result));
          }
        },
        jsify({'remember': remember})
      ]);
      return c.future;
  
negative.code:     // failure. On success, the first argument will be null and the second
      // will be an object containing { auth: <auth payload>, expires:
      // <expiration time in seconds since the unix epoch> }.
      _fb.callMethod(
          'authWithPassword', [jsify(credentials), _getAuthCallback(c)]);
      return c.future;
    }
  
  