anchor.diff:  import 'hit_test.dart';
   import 'object.dart';
   import 'view.dart';
  +
  +typedef void EventListener(InputEvent event);
  +typedef void MetricListener(Size size);
   
   int _hammingWeight(int value) {
     if (value == 0)
  
positive.code:   RenderView get renderView => _renderView;
    RenderView _renderView;
  
    ViewConstraints _createConstraints() {
      return new ViewConstraints(size: new Size(ui.view.width, ui.view.height));
    }
    void _handleMetricsChanged() {
      _renderView.rootConstraints = _createConstraints();
    }
  
    /// Pump the rendering pipeline to generate a frame for the given time stamp
  
negative.code:     if (ourEvent is PointerInputEvent) {
        _handlePointerInputEvent(ourEvent);
      } else {
        assert(event.type == 'back');
        for (EventListener listener in _eventListeners)
          listener(ourEvent);
      }
  