anchor.diff:      });
   
       _addWheelEventListener((html.Event event) {
  -      assert(event is html.WheelEvent);
  -      if (_debugLogPointerEvents) {
  -        print(event.type);
  -      }
  -      _callback(_convertWheelEventToPointerData(event as html.WheelEvent));
  -      // Prevent default so mouse wheel event doesn't get converted to
  -      // a scroll event that semantic nodes would process.
  -      event.preventDefault();
  +      _handleWheelEvent(event, _callback);
       });
     }
   
  
positive.code:     }, acceptOutsideGlasspane: true);
  
      _addWheelEventListener((html.Event event) {
        assert(event is html.WheelEvent);
        if (_debugLogPointerEvents) {
          print(event.type);
        }
        _callback(_convertWheelEventToPointerData(event as html.WheelEvent));
        // Prevent default so mouse wheel event doesn't get converted to
        // a scroll event that semantic nodes would process.
        event.preventDefault();
      });
    }
  
  
negative.code:     );
    }
  
    void _handleWheelEvent(
        html.Event e, void Function(Iterable<ui.PointerData>) sink) {
      assert(e is html.WheelEvent);
      final html.WheelEvent event = e as html.WheelEvent;
      if (_debugLogPointerEvents) {
        print(event.type);
      }
      if (event.getModifierState('Control') &&
          operatingSystem != OperatingSystem.macOs &&
          operatingSystem != OperatingSystem.iOs) {
        // Ignore Control+wheel events since the default handler
        // will change browser zoom level instead of scrolling.
        // The exception is MacOs where Control+wheel will still scroll and zoom
        // is not implemented.
        return;
      }
      _callback(_convertWheelEventToPointerData(event));
      // Prevent default so mouse wheel event doesn't get converted to
      // a scroll event that semantic nodes would process.
      //
      event.preventDefault();
    }
  
    /// For browsers that report delta line instead of pixels such as FireFox
    /// compute line height using the default font size.
    ///
  