Testing & supporting new HTMLTemplateElement

tools/dom/dom.json

 {
   "AbstractWorker": {
     "comment": "http://www.w3.org/TR/workers/#the-abstractworker-abstract-interface",
     "members": {
       "addEventListener": {},
       "dispatchEvent": {},
       "onerror": {},
       "removeEventListener": {}
     },
     "support_level": "stable"
@@ skipping 4645 matching lines @@
         "comment": "http://www.whatwg.org/specs/web-apps/current-work/multipage/obsolete.html#HTMLTableSectionElement-partial",
         "dart_action": "suppress",
         "support_level": "deprecated"
       }
     },
     "support_level": "stable"
   },
   "HTMLTemplateElement": {
     "comment": "https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html#template-element",
     "members": {
+      "HTMLTemplateElement": {},
       "content": {}
     },
     "support_level": "experimental"
   },
   "HTMLTextAreaElement": {
     "comment": "http://www.whatwg.org/specs/web-apps/current-work/multipage/the-button-element.html#the-textarea-element",
     "members": {
       "HTMLTextAreaElement": {},
       "autofocus": {},
       "checkValidity": {},
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       "importStylesheet": {},
       "removeParameter": {},
       "reset": {},
       "setParameter": {},
       "transformToDocument": {},
       "transformToFragment": {}
     },
     "support_level": "nonstandard"
   }
 }