code: function flush () {
              var i = 0;
              while (i < fnQueueLen) {
                  fn(fnQueue[i], fnQueue[i + 1]);
                  fnQueue[i++] = $undefined;
                  fnQueue[i++] = $undefined;
              }
  
              fnQueueLen = 0;
              if (fnQueue.length > initQueueSize) fnQueue.length = initQueueSize;
          }
docs: Run all queued functions.
  @private