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

Source/core/loader/DocumentLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * 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.
@@ skipping 756 matching lines @@
 const KURL& DocumentLoader::originalURL() const
 {
     return m_originalRequestCopy.url();
 }
 
 const KURL& DocumentLoader::requestURL() const
 {
     return request().url();
 }
 
-const String& DocumentLoader::responseMIMEType() const
+const AtomicString& DocumentLoader::responseMIMEType() const
 {
     return m_response.mimeType();
 }
 
 const KURL& DocumentLoader::unreachableURL() const
 {
     return m_substituteData.failingURL();
 }
 
 void DocumentLoader::setDefersLoading(bool defers)
@@ skipping 159 matching lines @@
 void DocumentLoader::replaceDocument(const String& source, Document* ownerDocument)
 {
     m_frame->loader().stopAllLoaders();
     m_writer = createWriterFor(m_frame, ownerDocument, m_frame->document()->url(), mimeType(), m_writer ? m_writer->encoding() : emptyAtom,  m_writer ? m_writer->encodingWasChosenByUser() : false, true);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 } // namespace WebCore