message: Avoid using the Graph owned FunctionLibraryDefinition in DirectSession
  This is part of a series of change intended to decouple the FunctionLibraryDefinition
  from the Graph entirely.
diff: @@ -1666,7 +1666,7 @@ Status DirectSession::CreateGraphs(
  // Just return '1'.
  return 1;
  };
  - popts.flib_def = &client_graph->graph.flib_def();
  + popts.flib_def = flib_def->get();
  popts.control_flow_added = false;
  std::unordered_map<string, GraphDef> partitions;
  