Type extension support in polyfill.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index a1ebcf2b23a15367c2fbb05781a2c7e5364711f4..175cf5c898f4bc59fa8532a507b5e9e77dfec0e2 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -8800,8 +8800,8 @@ abstract class Element extends Node implements ParentNode, ChildNode native "Ele
    *
    * * [isTagSupported]
    */
-  factory Element.tag(String tag) =>
-      _ElementFactoryProvider.createElement_tag(tag);
+  factory Element.tag(String tag, [String typeExtention]) =>
+      _ElementFactoryProvider.createElement_tag(tag, typeExtention);
 
   /// Creates a new `<a>` element.
   ///
@@ -9118,7 +9118,7 @@ abstract class Element extends Node implements ParentNode, ChildNode native "Ele
    * The tag should be a valid HTML tag name.
    */
   static bool isTagSupported(String tag) {
-    var e = _ElementFactoryProvider.createElement_tag(tag);
+    var e = _ElementFactoryProvider.createElement_tag(tag, null);
     return e is Element && !(e is UnknownElement);
   }
 
@@ -10554,9 +10554,9 @@ class _ElementFactoryProvider {
   @DomName('Document.createElement')
   // Optimization to improve performance until the dart2js compiler inlines this
   // method.
-  static dynamic createElement_tag(String tag) =>
-      // Firefox may return a JS function for some types (Embed, Object).
-      JS('Element|=Object', 'document.createElement(#)', tag);
+  static dynamic createElement_tag(String tag, String typeExtension) =>
+    // Firefox may return a JS function for some types (Embed, Object).
+    JS('Element|=Object', 'document.createElement(#, #)', tag, typeExtension);
 }
 
 
@@ -30810,6 +30810,79 @@ _makeCreatedCallbackMethod() {
       convertDartClosureToJS(_callCreated, 1));
 }
 
+const _typeNameToTag = const {
+  'HTMLAnchorElement': 'a',
+  'HTMLAppletElement': 'applet',
+  'HTMLAreaElement': 'area',
+  'HTMLAudioElement': 'audio',
+  'HTMLBRElement': 'br',
+  'HTMLBaseElement': 'base',
+  'HTMLBaseFontElement': 'basefont',
+  'HTMLBodyElement': 'body',
+  'HTMLButtonElement': 'button',
+  'HTMLCanvasElement': 'canvas',
+  'HTMLDListElement': 'dl',
+  'HTMLDataListElement': 'datalist',
+  'HTMLDirectoryElement': 'dir',
+  'HTMLDivElement': 'div',
+  'HTMLEmbedElement': 'embed',
+  'HTMLFieldSetElement': 'fieldset',
+  'HTMLFontElement': 'font',
+  'HTMLFormElement': 'form',
+  'HTMLFrameElement': 'frame',
+  'HTMLFrameSetElement': 'frameset',
+  'HTMLHRElement': 'hr',
+  'HTMLHeadElement': 'head',
+  'HTMLHeadingElement': 'h1',
+  'HTMLHtmlElement': 'html',
+  'HTMLIFrameElement': 'iframe',
+  'HTMLImageElement': 'image',
+  'HTMLImageElement': 'img',
+  'HTMLInputElement': 'input',
+  'HTMLKeygenElement': 'keygen',
+  'HTMLLIElement': 'li',
+  'HTMLLabelElement': 'label',
+  'HTMLLegendElement': 'legend',
+  'HTMLLinkElement': 'link',
+  'HTMLMapElement': 'map',
+  'HTMLMarqueeElement': 'marquee',
+  'HTMLMenuElement': 'menu',
+  'HTMLMetaElement': 'meta',
+  'HTMLMeterElement': 'meter',
+  'HTMLModElement': 'del',
+  'HTMLModElement': 'ins',
+  'HTMLOListElement': 'ol',
+  'HTMLObjectElement': 'object',
+  'HTMLOptGroupElement': 'optgroup',
+  'HTMLOptionElement': 'option',
+  'HTMLOutputElement': 'output',
+  'HTMLParagraphElement': 'p',
+  'HTMLParamElement': 'param',
+  'HTMLPreElement': 'pre',
+  'HTMLProgressElement': 'progress',
+  'HTMLQuoteElement': 'blockquote',
+  'HTMLQuoteElement': 'q',
+  'HTMLScriptElement': 'script',
+  'HTMLSelectElement': 'select',
+  'HTMLShadowElement': 'shadow',
+  'HTMLSourceElement': 'source',
+  'HTMLSpanElement': 'span',
+  'HTMLStyleElement': 'style',
+  'HTMLTableCaptionElement': 'caption',
+  'HTMLTableCellElement': 'td',
+  'HTMLTableColElement': 'col',
+  'HTMLTableElement': 'table',
+  'HTMLTableRowElement': 'tr',
+  'HTMLTableSectionElement': 'tbody',
+  'HTMLTableSectionElement': 'tfoot',
+  'HTMLTableSectionElement': 'thead',
+  'HTMLTextAreaElement': 'textarea',
+  'HTMLTitleElement': 'title',
+  'HTMLTrackElement': 'track',
+  'HTMLUListElement': 'ul',
+  'HTMLVideoElement': 'video',
+};
+
 void _registerCustomElement(context, document, String tag, Type type) {
   // Function follows the same pattern as the following JavaScript code for
   // registering a custom element.
@@ -30852,8 +30925,15 @@ void _registerCustomElement(context, document, String tag, Type type) {
 
   setNativeSubclassDispatchRecord(proto, interceptor);
 
-  JS('void', '#.register(#, #)',
-      document, tag, JS('', '{prototype: #}', proto));
+  var options = JS('=Object', '{prototype: #}', proto);
+
+  if (baseClassName != 'HTMLElement') {
+    if (_typeNameToTag.containsKey(baseClassName)) {
+      JS('=Object', '#.extends = #', options, _typeNameToTag[baseClassName]);
+    }
+  }
+
+  JS('void', '#.register(#, #)', document, tag, options);
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a