Update HTMLFormControlsCollection's named getter to behave according to spec

Source/core/html/HTMLCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. 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.
@@ skipping 508 matching lines @@
         if (!idAttribute.isEmpty()) {
             HashSet<AtomicString>::AddResult addResult = existingNames.add(idAttribute);
             if (addResult.isNewEntry)
                 names.append(idAttribute);
         }
     }
 }
 
 void HTMLCollection::namedPropertyEnumerator(Vector<String>& names, ExceptionState&)
 {
-    return supportedPropertyNames(names);
+    supportedPropertyNames(names);
 }
 
 void HTMLCollection::updateNameCache() const
 {
     if (hasNameCache())
         return;
 
     ContainerNode& root = rootNode();
     for (Element* element = traverseToFirstElement(root); element; element = traverseNextElement(*element, root)) {
         const AtomicString& idAttrVal = element->getIdAttribute();
@@ skipping 29 matching lines @@
 
 void HTMLCollection::append(NodeCacheMap& map, const AtomicString& key, Element* element)
 {
     OwnPtr<Vector<Element*> >& vector = map.add(key.impl(), nullptr).iterator->value;
     if (!vector)
         vector = adoptPtr(new Vector<Element*>);
     vector->append(element);
 }
 
 } // namespace WebCore