* TODO(cpovirk): Maybe it would be cleaner to define a CancellationSupplier interface
               * with two implementations, one that contains causeless Cancellation instances and
               * the other of which creates new Cancellation instances each time it's called? Yet
               * another alternative is to fill in a non-null value for each of the fields no matter

      listener.execute();
    }
    listeners = null;
  }

  protected void afterDone() {}

  @Override
  protected final Throwable tryInternalFastPathGetFailure() {
    if (this instanceof Trusted) {
      return state == State.FAILURE ? throwable : null;
    }
    return null;
  }

  final void maybePropagateCancellationTo(@Nullable Future<?> related) {