String closingFutureToString() {
      // TODO(dpb): Better toString, in the style of Futures.transform etc.
      return toStringHelper("ClosingFuture")
          .add("status", status.get())
          .addValue(future)
          .toString();
    }
  }

  // TODO(dpb): Should we use a pair of ArrayLists instead of an IdentityHashMap?

    public static final String LABELS_web_api_json_enabled = "{labels.web_api_json_enabled}";

    /** The key of the message: System Property */
    public static final String LABELS_app_value = "{labels.app_value}";

    /** The key of the message: Default Label Value */
    public static final String LABELS_default_label_value = "{labels.default_label_value}";

    /** The key of the message: Default Sort Value */