Removing dart2js's extends tag inference

tools/dom/src/dart2js_CustomElementSupport.dart

Index: tools/dom/src/dart2js_CustomElementSupport.dart
diff --git a/tools/dom/src/dart2js_CustomElementSupport.dart b/tools/dom/src/dart2js_CustomElementSupport.dart
index 8edecc44a8edc2fd472ef40f9c7234c5a7b5dab6..6f8aedb2e3352186ffb1583bd908cf845e8dc7df 100644
--- a/tools/dom/src/dart2js_CustomElementSupport.dart
+++ b/tools/dom/src/dart2js_CustomElementSupport.dart
@@ -41,30 +41,6 @@ _makeCallbackMethod3(callback) {
       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
@@ -133,8 +109,6 @@ void _registerCustomElement(context, document, String tag, Type type,
   if (baseClassName != 'HTMLElement') {
     if (extendsTagName != null) {
       JS('=Object', '#.extends = #', options, extendsTagName);
-    } else if (_typeNameToTag.containsKey(baseClassName)) {
-      JS('=Object', '#.extends = #', options, _typeNameToTag[baseClassName]);
     }
   }