anchor.diff:  /// function in BindableList.
   class ComputedMappedBindableList<T, O> extends MappedBindableList<T, O> {
       List<StreamSubscription> _subscribers = [];
  +    List<StreamSubscription> _invalidationSubscribers = [];
       List<Bindable> _mapInputs = [];
   
       /// Arguments to the map function are [mapItem, input1, input2, ...]
  
positive.code:             this._mapBindable.value = mapFunction;
              this._mappedChangeStream = this._input.changeStream.map(_mapChangeRecord);
              this._inputChanges = this._mappedChangeStream.listen(_onInputChange);
  
              this._mapBindable.changeStream.listen((c) {
                  this.listInstance.replaceRange(
  
negative.code: class MappedBindableList<T, O> extends FixedBindableList<T> {
      Stream<ChangeRecord> _mappedChangeStream;
      StreamSubscription<ChangeRecord> _inputChanges;
      StreamSubscription _basisInvalidationListener;
      final BaseBindableList<O> _input;
      Bindable<Function> _mapBindable = new Bindable((c) => null);
  
  