anchor.diff:      }
     }
   
  -  void _updatePaintingCanvas() {
  +  void _repaint() {
       assert(!_needsLayout);
  -    assert(createNewDisplayList);
  +    assert(requiresCompositing);
       sky.PictureRecorder recorder = new sky.PictureRecorder();
       sky.Canvas canvas = new sky.Canvas(recorder, paintBounds);
       PaintingContext context = new PaintingContext(canvas);
  
positive.code:     assert(!debugDoingPaint);
      if (!attached) return; // Don't try painting things that aren't in the hierarchy
      if (_needsPaint) return;
      if (createNewDisplayList) {
        _needsPaint = true;
        _nodesNeedingPaint.add(this);
        scheduler.ensureVisualUpdate();
  
negative.code: 
    PaintingContext(this.canvas);
  
    void paintChild(RenderObject child, Point point) {
      // TODO(abarth): Support compositing.
      assert(!child.requiresCompositing);
      child._paintWithContext(this, point.toOffset());
    }
  }
  
  