Update HTTPHeaderMap wrappers to use AtomicString type for header values

Source/wtf/text/StringOperators.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
  *
  * 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 17 matching lines @@
 class StringAppend {
 public:
     StringAppend(StringType1 string1, StringType2 string2)
         : m_string1(string1)
         , m_string2(string2)
     {
     }
 
     operator String() const
     {
-        RefPtr<StringImpl> resultImpl = makeString(m_string1, m_string2);
-        return resultImpl.release();
+        return String(makeString(m_string1, m_string2));
     }
 
     operator AtomicString() const
     {
-        return operator String();
+        return AtomicString(makeString(m_string1, m_string2));
     }
 
     bool is8Bit()
     {
         StringTypeAdapter<StringType1> adapter1(m_string1);
         StringTypeAdapter<StringType2> adapter2(m_string2);
         return adapter1.is8Bit() && adapter2.is8Bit();
     }
 
     void writeTo(LChar* destination)
@@ skipping 84 matching lines @@
 
 template<typename U, typename V, typename W>
 StringAppend<StringAppend<U, V>, W> operator+(const StringAppend<U, V>& string1, W string2)
 {
     return StringAppend<StringAppend<U, V>, W>(string1, string2);
 }
 
 } // namespace WTF
 
 #endif // StringOperators_h