super(futures.size());
    this.futures = checkNotNull(futures);
    this.allMustSucceed = allMustSucceed;
    this.collectsValues = collectsValues;
  }

  @Override
  protected final void afterDone() {
    super.afterDone();

    ImmutableCollection<? extends Future<?>> localFutures = futures;
    releaseResources(OUTPUT_FUTURE_DONE); // nulls out `futures`

    if (isCancelled() & localFutures != null) {