Function task

test/deferredSynchronousTask.js:6–13

(callback)

  if (!counter) counter = {scheduled: 0};

  function task(callback) {
    if (deferrals) return deferrals.push({callback: callback, index: counter.scheduled++});
    try {
      callback(null, {active: ++active, index: counter.scheduled++});
    } finally {
      --active;
    }
  }

  task.finish = function() {
    var deferrals_ = deferrals.slice();