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

Source/core/html/HTMLMetaElement-in.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, 2010 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 453 matching lines @@
     if (equalIgnoringCase(nameValue, "viewport"))
         processViewportContentAttribute(contentValue, ViewportDescription::ViewportMeta);
     else if (equalIgnoringCase(nameValue, "referrer"))
         document().processReferrerPolicy(contentValue);
     else if (equalIgnoringCase(nameValue, "handheldfriendly") && equalIgnoringCase(contentValue, "true"))
         processViewportContentAttribute("width=device-width", ViewportDescription::HandheldFriendlyMeta);
     else if (equalIgnoringCase(nameValue, "mobileoptimized"))
         processViewportContentAttribute("width=device-width, initial-scale=1", ViewportDescription::MobileOptimizedMeta);
 }
 
-String HTMLMetaElement::content() const
+const AtomicString& HTMLMetaElement::content() const
 {
     return getAttribute(contentAttr);
 }
 
-String HTMLMetaElement::httpEquiv() const
+const AtomicString& HTMLMetaElement::httpEquiv() const
 {
     return getAttribute(http_equivAttr);
 }
 
-String HTMLMetaElement::name() const
+const AtomicString& HTMLMetaElement::name() const
 {
     return getNameAttribute();
 }
 
 }