Remove AtomicStringImpl.

Source/wtf/text/StringImpl.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. 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.
  *
@@ skipping 111 matching lines @@
     // This is needed because we malloc() space for a StringImpl plus an
     // immediately following buffer, as a performance tweak.
     NEW_DELETE_SAME_AS_MALLOC_FREE;
     friend struct WTF::CStringTranslator;
     template<typename CharacterType> friend struct WTF::HashAndCharactersTranslator;
     friend struct WTF::HashAndUTF8CharactersTranslator;
     friend struct WTF::CharBufferFromLiteralDataTranslator;
     friend struct WTF::LCharBufferTranslator;
     friend struct WTF::SubstringTranslator;
     friend struct WTF::UCharBufferTranslator;
-    friend class AtomicStringImpl;
 
 private:
     enum BufferOwnership {
         BufferInternal,
         BufferOwned,
         BufferSubstring,
         // NOTE: Adding more ownership types needs to extend m_hashAndFlags as we're at capacity
     };
 
     // Used to construct static strings, which have an special refCount that can never hit zero.
@@ skipping 1047 matching lines @@
 }
 
 using WTF::StringImpl;
 using WTF::equal;
 using WTF::equalNonNull;
 using WTF::TextCaseSensitivity;
 using WTF::TextCaseSensitive;
 using WTF::TextCaseInsensitive;
 
 #endif