Have HashMap<KeyType, AtomicString>::get() return a const reference

Source/platform/network/HTTPHeaderMap.cpp

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 48 matching lines @@
 void HTTPHeaderMap::adopt(PassOwnPtr<CrossThreadHTTPHeaderMapData> data)
 {
     clear();
     size_t dataSize = data->size();
     for (size_t index = 0; index < dataSize; ++index) {
         pair<String, String>& header = (*data)[index];
         set(AtomicString(header.first), AtomicString(header.second));
     }
 }
 
-AtomicString HTTPHeaderMap::get(const AtomicString& name) const
+const AtomicString& HTTPHeaderMap::get(const AtomicString& name) const
 {
     return HashMap<AtomicString, AtomicString, CaseFoldingHash>::get(name);
 }
 
 HTTPHeaderMap::AddResult HTTPHeaderMap::add(const AtomicString& name, const AtomicString& value)
 {
     return HashMap<AtomicString, AtomicString, CaseFoldingHash>::add(name, value);
 }
 
 // Adapter that allows the HashMap to take C strings as keys.
@@ skipping 26 matching lines @@
 {
     return find<CaseFoldingCStringTranslator>(name) != end();
 }
 
 HTTPHeaderMap::AddResult HTTPHeaderMap::add(const char* name, const AtomicString& value)
 {
     return HashMap<AtomicString, AtomicString, CaseFoldingHash>::add<CaseFoldingCStringTranslator>(name, value);
 }
 
 } // namespace WebCore