Use AtomicString type more consistently for mimeType / encoding

Source/platform/mhtml/ArchiveResource.h

 /*
  * Copyright (C) 2008, 2010 Apple 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
@@ skipping 23 matching lines @@
 #include "platform/weborigin/KURL.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 class PLATFORM_EXPORT ArchiveResource : public RefCounted<ArchiveResource> {
 public:
     static PassRefPtr<ArchiveResource> create(PassRefPtr<SharedBuffer>, const KURL&, const ResourceResponse&);
     static PassRefPtr<ArchiveResource> create(PassRefPtr<SharedBuffer>, const KURL&,
-        const String& mimeType, const String& textEncoding, const String& frameName,
+        const AtomicString& mimeType, const AtomicString& textEncoding, const String& frameName,
         const ResourceResponse& = ResourceResponse());
 
     const KURL& url() const { return m_url; }
     const ResourceResponse& response() const { return m_response; }
     SharedBuffer* data() const { return m_data.get(); }
-    const String& mimeType() const { return m_mimeType; }
-    const String& textEncoding() const { return m_textEncoding; }
+    const AtomicString& mimeType() const { return m_mimeType; }
+    const AtomicString& textEncoding() const { return m_textEncoding; }
     const String& frameName() const { return m_frameName; }
 
 private:
-    ArchiveResource(PassRefPtr<SharedBuffer>, const KURL&, const String& mimeType, const String& textEncoding, const String& frameName, const ResourceResponse&);
+    ArchiveResource(PassRefPtr<SharedBuffer>, const KURL&, const AtomicString& mimeType, const AtomicString& textEncoding, const String& frameName, const ResourceResponse&);
 
     KURL m_url;
     ResourceResponse m_response;
     RefPtr<SharedBuffer> m_data;
-    String m_mimeType;
-    String m_textEncoding;
+    AtomicString m_mimeType;
+    AtomicString m_textEncoding;
     String m_frameName;
 };
 
 }
 
 #endif // ArchiveResource_h