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

Source/platform/network/HTTPHeaderMap.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * 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:
  * 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 33 matching lines @@
 class PLATFORM_EXPORT HTTPHeaderMap : public HashMap<AtomicString, AtomicString, CaseFoldingHash> {
 public:
     HTTPHeaderMap();
     ~HTTPHeaderMap();
 
     // Gets a copy of the data suitable for passing to another thread.
     PassOwnPtr<CrossThreadHTTPHeaderMapData> copyData() const;
 
     void adopt(PassOwnPtr<CrossThreadHTTPHeaderMapData>);
 
-    AtomicString get(const AtomicString& name) const;
+    const AtomicString& get(const AtomicString& name) const;
 
     AddResult add(const AtomicString& name, const AtomicString& value);
 
     // Alternate accessors that are faster than converting the char* to AtomicString first.
     bool contains(const char*) const;
     const AtomicString& get(const char*) const;
     AddResult add(const char* name, const AtomicString& value);
 
 };
 
 } // namespace WebCore
 
 #endif // HTTPHeaderMap_h