message: Explicitely place the swap-in node: this ensures that subsequent rounds of
  memory optimization have a more accurate picture of the placement.
diff: @@ -730,6 +730,7 @@ Status BuildSwapPair(NodeDef* node, int input_to_swap,
  *swap_in_node->add_input() = swap_out_node->name();
  // Colocate the swap_in_ node with the node itself.
  + swap_in_node->set_device(node->device());
  string coloc_group = strings::StrCat("loc@", tensor_to_swap);
  (*swap_in_node->mutable_attr())["_class"].mutable_list()->add_s(coloc_group);
  (*node->mutable_attr())["_class"].mutable_list()->add_s(coloc_group);
  