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

Source/core/rendering/HitTestResult.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 82 matching lines @@
     void setInnerNonSharedNode(Node*);
     void setURLElement(Element*);
     void setScrollbar(Scrollbar*);
     void setIsFirstLetter(bool b) { m_isFirstLetter = b; }
     void setIsOverWidget(bool b) { m_isOverWidget = b; }
 
     Frame* targetFrame() const;
     bool isSelected() const;
     String spellingToolTip(TextDirection&) const;
     String title(TextDirection&) const;
-    String altDisplayString() const;
+    const AtomicString& altDisplayString() const;
     String titleDisplayString() const;
     Image* image() const;
     IntRect imageRect() const;
     KURL absoluteImageURL() const;
     KURL absoluteMediaURL() const;
     KURL absoluteLinkURL() const;
     String textContent() const;
     bool isLiveLink() const;
     bool isMisspelled() const;
     bool isContentEditable() const;
@@ skipping 28 matching lines @@
     RefPtr<Scrollbar> m_scrollbar;
     bool m_isOverWidget; // Returns true if we are over a widget (and not in the border/padding area of a RenderWidget for example).
     bool m_isFirstLetter;
 
     mutable OwnPtr<NodeSet> m_rectBasedTestResult;
 };
 
 } // namespace WebCore
 
 #endif // HitTestResult_h