anchor.diff:  // Use of this source code is governed by a BSD-style license that can be
   // found in the LICENSE file.
   
  -library layout;
  -
  -// This version of layout.dart is an update to the other one, this one using new APIs.
  -// It will not work in a stock Sky setup currently.
  -
   import 'node.dart';
  -
   import 'dart:sky' as sky;
   
   // ABSTRACT LAYOUT
  
positive.code:     RenderBox root,
      this.timeForRotation: const Duration(microseconds: 83333)
    }) {
      assert(root != null);
      this.root = root;
    }
  
  
negative.code:   RenderBox _root;
    RenderBox get root => _root;
    void set root (RenderBox value) {
      if (_root != null)
        dropChild(_root);
      _root = value;
      if (_root != null)
        adoptChild(_root);
      markNeedsLayout();
    }
  
  