anchor.diff:      _childrenHeight = y;
     }
   
  -  void hitTestChildren(HitTestResult result, { Point position }) {
  -    defaultHitTestChildren(result, position: position);
  -  }
  -
  -  void paint(PaintingCanvas canvas, Offset offset) {
  -    defaultPaint(canvas, offset);
  -  }
  -
   }
   
   class RenderBlock extends RenderBlockBase {
  
positive.code:   double getMaxIntrinsicHeight(BoxConstraints constraints) {
      return constraints.constrainHeight();
    }
  
    bool get sizedByParent => true;
  
  
negative.code: 
    double getMaxIntrinsicHeight(BoxConstraints constraints) {
      return _getIntrinsicHeight(constraints);
    }
  
    double computeDistanceToActualBaseline(TextBaseline baseline) {
      return defaultComputeDistanceToFirstActualBaseline(baseline);
    }
  
    bool _hasVisualOverflow = false;
  