[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/html/HTMLOptGroupElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 125 matching lines @@
     String itemText = document()->displayStringModifiedByEncoding(getAttribute(labelAttr));
     
     // In WinIE, leading and trailing whitespace is ignored in options and optgroups. We match this behavior.
     itemText = itemText.stripWhiteSpace();
     // We want to collapse our whitespace too.  This will match other browsers.
     itemText = itemText.simplifyWhiteSpace();
         
     return itemText;
 }
     
-HTMLSelectElement* HTMLOptGroupElement::ownerSelectElement() const
+Result<HTMLSelectElement> HTMLOptGroupElement::ownerSelectElement() const
 {
     ContainerNode* select = parentNode();
     while (select && !select->hasTagName(selectTag))
         select = select->parentNode();
     
     if (!select)
-       return 0;
+        return nullptr;
     
     return toHTMLSelectElement(select);
 }
 
 void HTMLOptGroupElement::accessKeyAction(bool)
 {
-    HTMLSelectElement* select = ownerSelectElement();
+    Handle<HTMLSelectElement> select = ownerSelectElement();
     // send to the parent to bring focus to the list box
     if (select && !select->focused())
         select->accessKeyAction(false);
 }
 
 } // namespace