SetFuture(AbstractFuture<V> owner, ListenableFuture<? extends V> future) {
      this.owner = owner;
      this.future = future;
    }

    @Override
    public void run() {
      if (owner.value != this) {
        // nothing to do, we must have been cancelled, don't bother inspecting the future.
        return;
      }
      Object valueToSet = getFutureValue(future);