anchor.diff:      _instance = this;
       ui.window.onMetricsChanged = handleMetricsChanged;
       initRenderView();
  +    assert(renderView != null);
       assert(() {
         initServiceExtensions();
         return true;
  
positive.code: 
    /// Pump the rendering pipeline to generate a frame.
    void beginFrame() {
      RenderObject.flushLayout();
      _renderView.updateCompositingBits();
      RenderObject.flushPaint();
      _renderView.compositeFrame();
    }
  
    void hitTest(HitTestResult result, Point position) {
      _renderView.hitTest(result, position: position);
      super.hitTest(result, position);
    }
  }
  
  /// Prints a textual representation of the entire render tree.
  void debugDumpRenderTree() {
    debugPrint(Renderer.instance.renderView.toStringDeep());
  }
  
  /// Prints a textual representation of the entire layer tree.
  void debugDumpLayerTree() {
    debugPrint(Renderer.instance.renderView.layer.toStringDeep());
  }
  
  /// A concrete binding for applications that use the Rendering framework
  /// directly. This is the glue that binds the framework to the Flutter engine.
  class RenderingFlutterBinding extends BindingBase with Scheduler, Renderer, Gesturer {
    RenderingFlutterBinding({ RenderBox root }) {
      renderView.child = root;
    }
  }
  
negative.code:       renderView = new RenderView();
        renderView.scheduleInitialFrame();
      }
      handleMetricsChanged(); // configures renderView's metrics
    }
  
    /// The render tree that's attached to the output surface.
    RenderView get renderView => _renderView;
    RenderView _renderView;
    void set renderView(RenderView value) {
      assert(value != null);
      if (_renderView == value)
        return;
      if (_renderView != null)
        _renderView.detach();
      _renderView = value;
      _renderView.attach();
    }
  
    void handleMetricsChanged() {
      assert(renderView != null);
      renderView.rootConstraints = new ViewConstraints(size: ui.window.size);
    }
  
    void _handlePersistentFrameCallback(Duration timeStamp) {
  