anchor.diff:  }
   
   void jsOnBenchmark(dynamic listener) {
  -  js_util.setProperty(html.window, '_flutter_internal_on_benchmark', listener);
  +  js_util.setProperty(html.window, '_flutter_internal_on_benchmark', listener != null ? js.allowInterop(listener) : null);
   }
  
positive.code:     });
      expect(
        () => Profiler.instance.benchmark('foo', 123),
        throwsA(isA<TypeError>()),
      );
      expect(data, isEmpty);
  
      // Not even a callback.
      jsOnBenchmark('string');
      expect(
        () => Profiler.instance.benchmark('foo', 123),
        throwsA(isA<TypeError>()),
      );
    });
  
negative.code: 
  // @dart = 2.6
  import 'dart:html' as html;
  import 'dart:js' as js;
  import 'dart:js_util' as js_util;
  
  import 'package:test/bootstrap/browser.dart';
  