message: Prevent a bool field from being accessed when uninitialized.
diff: @@ -353,7 +353,7 @@ class InMemoryRunGraphRequest : public MutableRunGraphRequestWrapper {
  private:
  string session_handle_;
  - bool create_worker_session_called_;
  + bool create_worker_session_called_ = false;
  string graph_handle_;
  int64 step_id_;
  ExecutorOpts exec_opts_;
  