Sync the DOMTokenList interface with the spec

https://dom.spec.whatwg.org/#interface-domtokenlist

BUG=460722

Review URL: https://codereview.chromium.org/947833002

git-svn-id: svn://svn.chromium.org/blink/trunk@190649 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/dom/DOMTokenList.idl

@@ -23,6 +23,7 @@
  */
 
 // https://dom.spec.whatwg.org/#interface-domtokenlist
+
 [
     SetWrapperReferenceFrom=element,
     WillBeGarbageCollected,
@@ -33,7 +34,7 @@
     [RaisesException, CustomElementCallbacks] void add(DOMString... tokens);
     [RaisesException, CustomElementCallbacks] void remove(DOMString... tokens);
     [RaisesException, CustomElementCallbacks] boolean toggle(DOMString token, optional boolean force);
-
+    // FIXME: stringifier should be enumerable.
     [NotEnumerable] stringifier;
     iterable<DOMString>;
 };