message: Fix TPU `saved_model.save` with SyncOnReadVariable.
diff: @@ -672,8 +672,6 @@ class TPUExtended(distribute_lib.StrategyExtendedV1):
  reduce_op, value, destinations, self._num_replicas_in_sync)
  # TODO(cjfj): Detect when it is possible to use `cross_replica_sum`.
  - # Always performs the reduction on the TPU host.
  - with ops.device(self._host_device):
  output = math_ops.add_n(value.values)
  if reduce_op == reduce_util.ReduceOp.MEAN:
  output *= (1. / len(value.values))
  