Consistently use AtomicString for namespaceURI / prefix

Source/core/dom/Node.h

 /*
  * 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, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.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 192 matching lines @@
     virtual PassRefPtr<Node> cloneNode(bool deep = false) = 0;
     virtual const AtomicString& localName() const;
     virtual const AtomicString& namespaceURI() const;
     virtual const AtomicString& prefix() const;
     virtual void setPrefix(const AtomicString&, ExceptionState&);
     void normalize();
 
     bool isSameNode(Node* other) const { return this == other; }
     bool isEqualNode(Node*) const;
     bool isDefaultNamespace(const AtomicString& namespaceURI) const;
-    String lookupPrefix(const AtomicString& namespaceURI) const;
-    String lookupNamespaceURI(const String& prefix) const;
-    String lookupNamespacePrefix(const AtomicString& namespaceURI, const Element* originalElement) const;
+    const AtomicString& lookupPrefix(const AtomicString& namespaceURI) const;
+    const AtomicString& lookupNamespaceURI(const String& prefix) const;
+    const AtomicString& lookupNamespacePrefix(const AtomicString& namespaceURI, const Element* originalElement) const;
 
     String textContent(bool convertBRsToNewlines = false) const;
     void setTextContent(const String&);
 
     Node& lastDescendant() const;
 
     // Other methods (not part of DOM)
 
     bool isElementNode() const { return getFlag(IsElementFlag); }
     bool isContainerNode() const { return getFlag(IsContainerFlag); }
@@ skipping 726 matching lines @@
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const WebCore::Node*);
 void showNodePath(const WebCore::Node*);
 #endif
 
 #endif