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()}.
   *

  private static final @Nullable Method getStackTraceDepthMethod =
      (jla == null) ? null : getSizeMethod(jla);

  /**
   * Returns the JavaLangAccess class that is present in all Sun JDKs. It is not allowed in
   * AppEngine, and not present in non-Sun JDKs.
   */
  @SuppressWarnings("removal") // b/318391980
  @J2ktIncompatible
  @GwtIncompatible // java.lang.reflect
  private static @Nullable Object getJla() {
    try {
      /*