anchor.diff:      return (elapsedTicks * 1000) ~/ frequency;
     }
   
  -  /**
  -   * Returns the frequency of the elapsed counter in Hz.
  -   */
  -  int get frequency => _frequency();
   
     /**
      * Returns wether the [StopWatch] is currently running.
  
positive.code:  * A simple stopwatch interface to measure elapsed time.
   */
  class Stopwatch {
    // The _start and _stop fields capture the time when [start] and [stop]
    // are called respectively.
    // If _start is null, then the [Stopwatch] has not been started yet.
  
negative.code:    *
     *     Stopwatch stopwatch = new Stopwatch()..start();
     */
    Stopwatch();
  
    /**
     * Starts the [Stopwatch].
  