message: Put overflowCount in the right place
diff: @@ -54,6 +54,7 @@ class QueuePool {
  // onto the queue pool. We want to return a promise which resolves
  // after the item has finished executing on the queue pool, hence
  // the promise chain here.
  + this._overflowCount++;
  return this.overflow.enqueue(id, {
  id: id,
  item: item,
  @@ -72,7 +73,6 @@ class QueuePool {
  p: queue.enqueue(req.id, req.item)
  });
  }
  - this._overflowCount++;
  // wait for any queue to become available
  let promises = this.queues.map((q) => {
  return q.onceFree();
  