if (bubbledTo == vacated) {
      // Could not bubble toTrickle up min levels, try moving
      // it from min level to max level (or max to min level) and bubble up
      // there.
      return heap.tryCrossOverAndBubbleUp(index, vacated, toTrickle);
    } else {
      return (bubbledTo < index) ? new MoveDesc<E>(toTrickle, elementData(index)) : null;
    }
  }

  // Returned from removeAt() to iterator.remove()