anchor.diff:    int alpha;
   
     void addToScene(ui.SceneBuilder builder, Offset layerOffset) {
  -    builder.pushOpacity(alpha, bounds?.shift(layerOffset));
  -    addChildrenToScene(builder, offset + layerOffset);
  +    Offset childOffset = offset + layerOffset;
  +    builder.pushOpacity(alpha, bounds?.shift(childOffset));
  +    addChildrenToScene(builder, childOffset);
       builder.pop();
     }
   
  
positive.code: 
    void addToScene(ui.SceneBuilder builder, Offset layerOffset) {
      assert(optionsMask != null);
      builder.addStatistics(optionsMask, paintBounds.shift(layerOffset));
      builder.setRasterizerTracingThreshold(rasterizerThreshold);
    }
  }
  
negative.code:   }
  
    /// Uploads all of this layer's children to the engine
    void addChildrenToScene(ui.SceneBuilder builder, Offset childOffset) {
      Layer child = _firstChild;
      while (child != null) {
        child.addToScene(builder, childOffset);
        child = child.nextSibling;
      }
    }
  