anchor.diff:  
     _scheduleTimer(Zone self, ZoneDelegate parent, Zone zone) {
   
  -    if(!_waitingForTimer && _advancingTo != null) {
  +    if (!_waitingForTimer && _advancingTo != null) {
         var next = _getNextTimer();
         var completeTimer = next != null ?
             self.bindCallback(() => _runTimer(next), runGuarded: true) :
  
positive.code:       });
  
    _advanceTo(DateTime to) {
      if(to.millisecondsSinceEpoch > _now.millisecondsSinceEpoch) {
        _now = to;
      }
    }
  
negative.code:   _runTimer(_FakeTimer timer) {
      assert(timer.isActive);
      _advanceTo(timer._nextCall);
      if (timer._isPeriodic) {
        timer._callback(timer);
        timer._nextCall = timer._nextCall.add(timer._duration);
      } else {
  