Implement "replacement" text encoding.

Source/modules/encoding/TextDecoder.h

 /*
  * Copyright (C) 2013 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 38 matching lines @@
     ~TextDecoder();
 
     // Implement the IDL
     String encoding() const;
     String decode(ArrayBufferView*, const Dictionary&, ExceptionState&);
     String decode(ExceptionState& exceptionState) { return decode(0, Dictionary(), exceptionState); }
 
     void trace(Visitor*) { }
 
 private:
-    TextDecoder(const String& encoding, bool fatal);
+    TextDecoder(const String& label, const String& name, bool fatal);
 
-    WTF::TextEncoding m_encoding;
+    String m_encoding;
     OwnPtr<WTF::TextCodec> m_codec;
     bool m_fatal;
     bool m_bomSeen;
 };
 
 } // namespace WebCore
 
 #endif // TextDecoder_h