Make sure getAttribute() / setAttribute() callers use AtomicStrings

Source/core/html/HTMLTableElement.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2010, 2011 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
@@ skipping 545 matching lines @@
 PassRefPtr<HTMLCollection> HTMLTableElement::rows()
 {
     return ensureCachedHTMLCollection(TableRows);
 }
 
 PassRefPtr<HTMLCollection> HTMLTableElement::tBodies()
 {
     return ensureCachedHTMLCollection(TableTBodies);
 }
 
-String HTMLTableElement::rules() const
+const AtomicString& HTMLTableElement::rules() const
 {
     return getAttribute(rulesAttr);
 }
 
-String HTMLTableElement::summary() const
+const AtomicString& HTMLTableElement::summary() const
 {
     return getAttribute(summaryAttr);
 }
 
 void HTMLTableElement::addSubresourceAttributeURLs(ListHashSet<KURL>& urls) const
 {
     HTMLElement::addSubresourceAttributeURLs(urls);
 
     addSubresourceURL(urls, document().completeURL(getAttribute(backgroundAttr)));
 }
 
 }