Use AtomicString API directly

Source/core/html/HTMLLinkElement.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) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Rob Buis (rwlbuis@gmail.com)
  * Copyright (C) 2011 Google 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 156 matching lines @@
     } else if (name == hrefAttr) {
         process();
     } else if (name == typeAttr) {
         m_type = value;
         process();
     } else if (name == sizesAttr) {
         m_sizes->setValue(value);
         parseSizesAttribute(value, m_iconSizes);
         process();
     } else if (name == mediaAttr) {
-        m_media = value.string().lower();
+        m_media = value.lower();
         process();
     } else if (name == disabledAttr) {
         if (LinkStyle* link = linkStyle())
             link->setDisabledState(!value.isNull());
     } else {
         if (name == titleAttr) {
             if (LinkStyle* link = linkStyle())
                 link->setSheetTitle(value);
         }
 
@@ skipping 550 matching lines @@
         removePendingSheet();
 }
 
 void LinkStyle::trace(Visitor* visitor)
 {
     visitor->trace(m_sheet);
     LinkResource::trace(visitor);
 }
 
 } // namespace blink