anchor.diff:      if (ourEvent is PointerInputEvent) {
         _handlePointerInputEvent(ourEvent);
       } else {
  +      assert(event.type == 'back');
         for (EventListener listener in _eventListeners)
           listener(ourEvent);
       }
  
positive.code: import 'hit_test.dart';
  import 'object.dart';
  import 'view.dart';
  
  int _hammingWeight(int value) {
    if (value == 0)
  
negative.code:     if (renderViewOverride == null) {
        _renderView = new RenderView(child: root);
        _renderView.attach();
        _handleMetricsChanged();
        _renderView.scheduleInitialFrame();
      } else {
        _renderView = renderViewOverride;
  