anchor.diff:    }
   }
   
  -typedef Widget Builder();
  -
   class RenderBoxToWidgetAdapter extends AbstractWidgetRoot {
   
     RenderBoxToWidgetAdapter(
  
positive.code:       String lastPrefix = prefix + '   ';
        childrenString += lastChild.toString(lastPrefix, lastStartPrefix);
      }
      if (key == null)
        return '$startPrefix$runtimeType(unkeyed)\n$childrenString';
      return '$startPrefix$runtimeType("$key")\n$childrenString';
    }
  
  }
  
negative.code: Set<Component> _dirtyComponents = new Set<Component>();
  bool _buildScheduled = false;
  bool _inRenderDirtyComponents = false;
  int _inLayoutCallbackBuilder = 0;
  
  class LayoutCallbackBuilderHandle { bool _active = true; }
  LayoutCallbackBuilderHandle enterLayoutCallbackBuilder() {
    if (!inDebugBuild)
      return null;
    _inLayoutCallbackBuilder += 1;
    return new LayoutCallbackBuilderHandle();
  }
  void exitLayoutCallbackBuilder(LayoutCallbackBuilderHandle handle) {
    if (!inDebugBuild)
      return;
    assert(handle._active);
    handle._active = false;
    _inLayoutCallbackBuilder -= 1;
  }
  
  List<int> _debugFrameTimes = <int>[];
  
  