refresh () {
    // In the special case that the timer is not in the list of active timers,
    // add it back to the array to be processed in the next tick by the onTick
    // function.
    if (this._state === NOT_IN_LIST) {
      fastTimers.push(this)
    }

    // If the timer is the only active timer, refresh the fastNowTimeout for
    // better resolution.
    if (!fastNowTimeout || fastTimers.length === 1) {
      refreshTimeout()
    }

    // Setting the state to PENDING will cause the timer to be reset in the
    // next tick by the onTick function.
    this._state = PENDING
  }
Sets the timer's start time to the current time, and reschedules the timer
to call its callback at the previously specified duration adjusted to the
current time.
Using this on a timer that has already called its callback will reactivate
the timer.

@returns {void}