anchor.diff:    void didReplace(Route oldRoute) {
       if (oldRoute is TransitionRoute)
         _controller.value = oldRoute._controller.value;
  -    _animation.addStatusListener(handleStatusChanged);
  +    _animation.addStatusListener(_handleStatusChanged);
       super.didReplace(oldRoute);
     }
   
  
positive.code: 
    // The API for _ModalScope and HeroController
  
    bool get offstage => _offstage;
    bool _offstage = false;
    void set offstage (bool value) {
  
negative.code:     });
    }
  
    /// The build context for the subtree containing the primary content of this route.
    BuildContext get subtreeContext => _subtreeKey.currentContext;
  
  
  