Sync the NamedNodeMap interface with the spec

Source/core/dom/NamedNodeMap.idl

 /*
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
+// https://dom.spec.whatwg.org/#interface-namednodemap
+
 [
     SetWrapperReferenceFrom=element,
     TypeChecking=Interface,
     WillBeGarbageCollected,
 ] interface NamedNodeMap {
-
-    [MeasureAs=NamedNodeMapGetNamedItem] Attr getNamedItem(DOMString name);
-    [NotEnumerable, ImplementedAs=getNamedItem] getter Attr (DOMString name);
-
-    [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapSetNamedItem] Attr setNamedItem(Attr attr);
-
+    readonly attribute unsigned long length;
+    [MeasureAs=NamedNodeMapItem] getter Attr? item(unsigned long index);
+    // FIXME: getNamedItem should be an enumerable getter.
+    [MeasureAs=NamedNodeMapGetNamedItem] Attr? getNamedItem(DOMString name);
+    [NotEnumerable, ImplementedAs=getNamedItem] getter Attr? (DOMString name);
+    [MeasureAs=NamedNodeMapGetNamedItemNS] Attr? getNamedItemNS(DOMString? namespaceURI, DOMString localName);
+    [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapSetNamedItem] Attr? setNamedItem(Attr attr);
+    [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapSetNamedItemNS] Attr? setNamedItemNS(Attr attr);
     [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapRemoveNamedItem] Attr removeNamedItem(DOMString name);
-
-    [MeasureAs=NamedNodeMapItem] getter Attr item(unsigned long index);
-
-    readonly attribute unsigned long length;
-
-
-    // Introduced in DOM Level 2:
-
-    [MeasureAs=NamedNodeMapGetNamedItemNS] Attr getNamedItemNS(DOMString? namespaceURI, DOMString localName);
-
-    [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapSetNamedItemNS] Attr setNamedItemNS(Attr attr);
-
     [RaisesException, CustomElementCallbacks, MeasureAs=NamedNodeMapRemoveNamedItemNS] Attr removeNamedItemNS(DOMString? namespaceURI, DOMString localName);
-
 };