anchor.diff:  
   main() {
     useHtmlConfiguration();
  -  init.run();
  +  init.run().then((_) {
   
     var container = querySelector('#container') as DivElement;
   
  
positive.code:   test('basic custom element', () {
      container.append(new BasicElement());
      container.appendHtml('<basic-element></basic_element>');
      var elements = container.querySelectorAll('basic-element');
      for (var element in elements) {
        expect(element.runtimeType, BasicElement);
        expect(element.isBasicElement, isTrue);
      }
    });
  
    test('extends custom element', () {
      container.append(new ExtendedElement());
      container.appendHtml('<input is="extended-element" />');
      var elements = container.querySelectorAll('extended-element');
      for (var element in elements) {
        expect(element.runtimeType, ExtendedElement);
        expect(element.isExtendedElement, isTrue);
      }
    });
  }
  
negative.code: // BSD-style license that can be found in the LICENSE file.
  library custom_element_proxy_test;
  
  import 'dart:async';
  import 'dart:html';
  import 'dart:js';
  import 'package:initialize/initialize.dart' as init;
  