//    executing listeners in the order they were added
    // 3. push all the items onto 'onto' and return the new head of the stack
    Listener head = gasListeners(Listener.TOMBSTONE);
    Listener reversedList = onto;
    while (head != null) {
      Listener tmp = head;
      head = head.next;
      tmp.next = reversedList;
      reversedList = tmp;
    }