Implement "replacement" text encoding.

Source/wtf/text/TextCodecUTF8.h

 /*
  * Copyright (C) 2011 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef TextCodecUTF8_h
 #define TextCodecUTF8_h
 
 #include "wtf/text/TextCodec.h"
 
 namespace WTF {
 
-class TextCodecUTF8 FINAL : public TextCodec {
+class TextCodecUTF8 : public TextCodec {
 public:
     static void registerEncodingNames(EncodingNameRegistrar);
     static void registerCodecs(TextCodecRegistrar);
 
+protected:
+    TextCodecUTF8() : m_partialSequenceSize(0) { }
+
 private:
     static PassOwnPtr<TextCodec> create(const TextEncoding&, const void*);
-    TextCodecUTF8() : m_partialSequenceSize(0) { }
 
     virtual String decode(const char*, size_t length, FlushBehavior, bool stopOnError, bool& sawError) OVERRIDE;
     virtual CString encode(const UChar*, size_t length, UnencodableHandling) OVERRIDE;
     virtual CString encode(const LChar*, size_t length, UnencodableHandling) OVERRIDE;
 
     template<typename CharType>
     CString encodeCommon(const CharType* characters, size_t length);
 
     template <typename CharType>
     bool handlePartialSequence(CharType*& destination, const uint8_t*& source, const uint8_t* end, bool flush, bool stopOnError, bool& sawError);
     void handleError(UChar*& destination, bool stopOnError, bool& sawError);
     void consumePartialSequenceByte();
 
     int m_partialSequenceSize;
     uint8_t m_partialSequence[U8_MAX_LENGTH];
 
 };
 
 } // namespace WTF
 
 #endif // TextCodecUTF8_h