directExecutor());
    return future;
  }

  /**
   * Returns a default thread factory used to create new threads.
   *
   * <p>When running on AppEngine with access to <a
   * href="https://cloud.google.com/appengine/docs/standard/java/javadoc/">AppEngine legacy
   * APIs</a>, this method returns {@code ThreadManager.currentRequestThreadFactory()}. Otherwise,
   * it returns {@link Executors#defaultThreadFactory()}.
   *