anchor.diff:  
     _TravelingTimer({
       required _FakeTime owner,
  -    required DateTime createdInOriginalTime,
       required DateTime createdInFakeTime,
       required ZoneDelegate parent,
       required Zone zone,
       required Duration duration,
       required void Function() trigger,
     })  : _owner = owner,
  -        _createdInOriginalTime = createdInOriginalTime,
           _createdInFakeTime = createdInFakeTime,
           _parent = parent,
           _zone = zone,
  
positive.code: 
    /// Number of times this [_TravelingTimer] should have been triggered.
    int _tick = 0;
  
    /// [DateTime] when this [_TravelingTimer] is supposed to be triggered,
    /// measured in [_FakeTime._originalTime].
    DateTime get _elapsesAtInOriginalTime =>
        _createdInOriginalTime.add(_duration * (1 + tick));
  
    /// [DateTime] when this [_TravelingTimer] is supposed to be triggered,
    /// measured in [_FakeTime._fakeTime].
  
negative.code:   final _FakeTime _owner;
  
    /// [DateTime] when this [_TravelingTimer] was created in
    /// [_FakeTime._fakeTime].
    final DateTime _createdInFakeTime;
  
  