code: function insert(item, msecs) {
    item._idleStart = Timer.now();
    item._idleTimeout = msecs;
  
    if (msecs < 0) return;
  
    var list;
  
    if (lists[msecs]) {
      list = lists[msecs];
    } else {
      list = new Timer();
      list.start(msecs, 0);
  
      L.init(list);
  
      lists[msecs] = list;
      list.msecs = msecs;
      list[kOnTimeout] = listOnTimeout;
    }
  
    L.append(list, item);
    assert(!L.isEmpty(list)); // list is not empty
  }
docs: the main function - creates lists on demand and the watchers associated with them.