anchor.diff:  mojom.ViewProxy _initViewProxy() {
     int viewHandle = ui.takeViewHandle();
     assert(() {
  -    if (viewHandle == 0)
  +    if (viewHandle == core.MojoHandle.INVALID)
         debugPrint('Child view are supported only when running in Mojo shell.');
       return true;
     });
  
positive.code:     }
    }
  
    double get scale => _scale;
    double _scale;
    void set scale (double value) {
  
negative.code:       ..devicePixelRatio = scale;
      return (await _view.layoutChild(_viewKey, layoutParams)).info;
    }
  }
  
  /// (mojo-only) A view of a child application.
  class RenderChildView extends RenderBox {
    RenderChildView({
      ChildViewConnection child,
      double scale
    }) : _child = child, _scale = scale;
  
    /// The child to display.
    ChildViewConnection get child => _child;
    ChildViewConnection _child;
    void set child (ChildViewConnection value) {
  