  /**
   * Gets a scheduler that schedules work as soon as possible on the current thread.
   */
  var currentThreadScheduler = Scheduler.currentThread = (function () {
    var queue;

    function runTrampoline () {
      while (queue.length > 0) {
        var item = queue.dequeue();
        if (!item.isCancelled()) {
          !item.isCancelled() && item.invoke();
        }
      }
    }

    function scheduleNow(state, action) {
      var si = new ScheduledItem(this, state, action, this.now());

      if (!queue) {
        queue = new PriorityQueue(4);
        queue.enqueue(si);

        var result = tryCatch(runTrampoline)();
        queue = null;
        if (result === errorObj) { return thrower(result.e); }
      } else {
        queue.enqueue(si);
      }
      return si.disposable;
    }

    var currentScheduler = new Scheduler(defaultNow, scheduleNow, notSupported, notSupported);

    currentScheduler.scheduleRequired = function () { return !queue; };
    currentScheduler.ensureTrampoline = function (action) {
      if (!queue) { this.schedule(action); } else { action(); }
    };

    return currentScheduler;
  }());
