Port DocumentFragment to the new wrapperless DOM.

client/dom/templates/html/dartium/html_dartium.darttemplate

Index: client/dom/templates/html/dartium/html_dartium.darttemplate
diff --git a/client/dom/templates/html/dartium/html_dartium.darttemplate b/client/dom/templates/html/dartium/html_dartium.darttemplate
index cac92b170bfe4e4583b8059a9cace207a48c47e8..c2bfb436148c12c0315a4b85f242ce6b9b7f1465 100644
--- a/client/dom/templates/html/dartium/html_dartium.darttemplate
+++ b/client/dom/templates/html/dartium/html_dartium.darttemplate
@@ -78,6 +78,8 @@ _wrap(raw) {
       throw 'A document should never be wrapped directly. TODO(jacobr) XXX';
     case 'HTMLHtmlElement':
       return new _DocumentImpl._wrap(domObject);
+    case 'HTMLElement':
+      return new _UnknownElementImpl._wrap(domObject);
 $WRAPCASES
     default:
       throw 'Unrecognized object $domObject. Name=${domObject.typeName}';