Regression: Add back support for hr elements in select listbox

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 138 matching lines @@
     DEFINE_STATIC_LOCAL(AtomicString, labelMinHeight, ("1.2em", AtomicString::ConstructFromLiteral));
     RefPtrWillBeRawPtr<HTMLDivElement> label = HTMLDivElement::create(document());
     label->setAttribute(roleAttr, AtomicString("group", AtomicString::ConstructFromLiteral));
     label->setAttribute(aria_labelAttr, AtomicString());
     label->setInlineStyleProperty(CSSPropertyPadding, labelPadding);
     label->setInlineStyleProperty(CSSPropertyMinHeight, labelMinHeight);
     label->setIdAttribute(ShadowElementNames::optGroupLabel());
     root.appendChild(label);
 
     RefPtrWillBeRawPtr<HTMLContentElement> content = HTMLContentElement::create(document());
-    content->setAttribute(selectAttr, "option,optgroup");
+    content->setAttribute(selectAttr, "option,optgroup,hr");
     root.appendChild(content);
 }
 
 void HTMLOptGroupElement::updateGroupLabel()
 {
     const String& labelText = groupLabelText();
     HTMLDivElement& label = optGroupLabelElement();
     label.setTextContent(labelText);
     label.setAttribute(aria_labelAttr, AtomicString(labelText));
 }
 
 HTMLDivElement& HTMLOptGroupElement::optGroupLabelElement() const
 {
     return *toHTMLDivElement(userAgentShadowRoot()->getElementById(ShadowElementNames::optGroupLabel()));
 }
 
 } // namespace