anchor.diff:      RenderBox root,
       this.timeForRotation: const Duration(microseconds: 83333)
     }) {
  -    assert(root != null);
       this.root = root;
     }
   
  
positive.code:   }
  
    bool hitTest(HitTestResult result, { double x, double y }) {
      assert(root != null);
      if (x < 0.0 || x >= width || y < 0.0 || y >= height)
        return false;
      if (x >= 0.0 && x < root.width && y >= 0.0 && y < root.height)
        root.hitTest(result, x: x, y: y);
      result.add(this);
      return true;
    }
  
    void paint(RenderNodeDisplayList canvas) {
      canvas.paintChild(root, 0.0, 0.0);
    }
  
    void paintFrame() {
  
negative.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  import 'node.dart';
  import 'dart:sky' as sky;
  
  // ABSTRACT LAYOUT
  