anchor.diff:    AnimationPerformance _performance;
   
     void initState() {
  -    _position = new AnimatedType<Point>(_kTransitionStartPoint)
  -      ..end = Point.origin
  -      ..curve = easeOut;
  +    _position = new AnimatedType<Point>(
  +      _kTransitionStartPoint,
  +      end: Point.origin,
  +      curve: easeOut
  +    );
       _opacity = new AnimatedType<double>(0.0, end: 1.0)
         ..curve = easeOut;
       _performance = new AnimationPerformance()
  
positive.code:       if (content == null)
          continue;
        String key = historyEntry.route.key;
        Transition transition = new Transition(content: content, key: key)
          ..direction = (i <= state.historyIndex) ? TransitionDirection.forward : TransitionDirection.reverse
          ..interactive = (i == state.historyIndex)
          ..onDismissed = () {
          setState(() {
            state.history.remove(historyEntry);
          });
        };
        visibleRoutes.add(transition);
      }
      return new Stack(visibleRoutes);
  
negative.code:       direction = source.direction;
        _start();
      }
      interactive = source.interactive;
      onDismissed = source.onDismissed;
      super.syncFields(source);
    }
  