Removing dart2js's extends tag inference

tools/dom/src/dart2js_CustomElementSupport.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.dom.html;
 
 _callConstructor(constructor) {
   return (receiver) {
     return JS('', '#(#)', constructor, receiver);
   };
@@ skipping 23 matching lines @@
 _makeCallbackMethod3(callback) {
   return JS('',
       '''((function(invokeCallback) {
              return function(arg1, arg2, arg3) {
                return invokeCallback(this, arg1, arg2, arg3);
              };
           })(#))''',
       convertDartClosureToJS(callback, 4));
 }
 
-const _typeNameToTag = const {
-  'HTMLAnchorElement': 'a',
-  'HTMLAudioElement': 'audio',
-  'HTMLButtonElement': 'button',
-  'HTMLCanvasElement': 'canvas',
-  'HTMLDivElement': 'div',
-  'HTMLImageElement': 'img',
-  'HTMLInputElement': 'input',
-  'HTMLLIElement': 'li',
-  'HTMLLabelElement': 'label',
-  'HTMLMenuElement': 'menu',
-  'HTMLMeterElement': 'meter',
-  'HTMLOListElement': 'ol',
-  'HTMLOptionElement': 'option',
-  'HTMLOutputElement': 'output',
-  'HTMLParagraphElement': 'p',
-  'HTMLPreElement': 'pre',
-  'HTMLProgressElement': 'progress',
-  'HTMLSelectElement': 'select',
-  'HTMLSpanElement': 'span',
-  'HTMLUListElement': 'ul',
-  'HTMLVideoElement': 'video',
-};
-
 void _registerCustomElement(context, document, String tag, Type type,
     String extendsTagName) {
   // Function follows the same pattern as the following JavaScript code for
   // registering a custom element.
   //
   //    var proto = Object.create(HTMLElement.prototype, {
   //        createdCallback: {
   //          value: function() {
   //            window.console.log('here');
   //          }
@@ skipping 48 matching lines @@
 
   var interceptor = JS('=Object', '#.prototype', interceptorClass);
 
   setNativeSubclassDispatchRecord(proto, interceptor);
 
   var options = JS('=Object', '{prototype: #}', proto);
 
   if (baseClassName != 'HTMLElement') {
     if (extendsTagName != null) {
       JS('=Object', '#.extends = #', options, extendsTagName);
-    } else if (_typeNameToTag.containsKey(baseClassName)) {
-      JS('=Object', '#.extends = #', options, _typeNameToTag[baseClassName]);
     }
   }
 
   JS('void', '#.register(#, #)', document, tag, options);
 }
 
 //// Called by Element.created to do validation & initialization.
 void _initializeCustomElement(Element e) {
   // TODO(blois): Add validation that this is only in response to an upgrade.
 }