anchor.diff:    factory HeadingElement.h1() => document.createElement("h1");
     factory HeadingElement.h2() => document.createElement("h2");
     factory HeadingElement.h3() => document.createElement("h3");
  +}
  +
  +class ImageElement extends HtmlEment {
  +  String src;
   }
   
   class InputElement extends HtmlElement {
  
positive.code:   String src;
  }
  
  class ImageElement extends HtmlEment {
    String src;
  }
  
  class OptionElement extends HtmlElement {
    factory OptionElement({String data: '', String value : '', bool selected: false}) {
    }
  
negative.code: }
  
  class MediaElement extends Element {}
  
  class WindowBase {}
  
  class Window extends WindowBase {
    WindowBase open(String url, String name, [String options]) => null;
  }
  
  class NodeValidator {}
  
  class NodeTreeSanitizer {}
  
  class DocumentFragment {
    DocumentFragment.html(String html,
            {NodeValidator validator, NodeTreeSanitizer treeSanitizer}) {}
  }
  
  dynamic JS(a, b, c, d) {}
  ''',
  