protected boolean setFuture(ListenableFuture<? extends V> future) {
    checkNotNull(future);

    // If this future is already cancelled, cancel the delegate.
    // TODO(cpovirk): Should we do this at the end of the method, as in the server version?
    // TODO(cpovirk): Use maybePropagateCancellationTo?
    if (isCancelled()) {
      future.cancel(mayInterruptIfRunning);
    }

              /*
               * requireNonNull is safe because we've initialized these if
               * !GENERATE_CANCELLATION_CAUSES.
               *
               * TODO(cpovirk): Maybe it would be cleaner to define a CancellationSupplier interface
               * with two implementations, one that contains causeless Cancellation instances and