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

Source/core/html/HTMLTrackElement.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 97 matching lines @@
         track()->setLanguage(value);
     } else if (name == idAttr) {
         track()->setId(value);
     } else if (name == defaultAttr) {
         track()->setIsDefault(!value.isNull());
     }
 
     HTMLElement::parseAttribute(name, value);
 }
 
-String HTMLTrackElement::kind()
+const AtomicString& HTMLTrackElement::kind()
 {
     return track()->kind();
 }
 
-void HTMLTrackElement::setKind(const String& kind)
+void HTMLTrackElement::setKind(const AtomicString& kind)
 {
     setAttribute(kindAttr, kind);
 }
 
 LoadableTextTrack* HTMLTrackElement::ensureTrack()
 {
     if (!m_track) {
         // kind, label and language are updated by parseAttribute
         m_track = LoadableTextTrack::create(this);
     }
@@ skipping 173 matching lines @@
 HTMLMediaElement* HTMLTrackElement::mediaElement() const
 {
     Element* parent = parentElement();
     if (parent && parent->isMediaElement())
         return toHTMLMediaElement(parentNode());
     return 0;
 }
 
 }