Remove the Document.charset setter (making it readonly)

Source/core/loader/DocumentWriter.cpp

 /*
  * Copyright (C) 2010. Adam Barth. 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 101 matching lines @@
         m_parser->setDecoder(decoder.release());
     }
 
     // finish() can result replacing DocumentLoader::m_writer.
     RefPtrWillBeRawPtr<DocumentWriter> protectingThis(this);
     m_parser->finish();
     m_parser = nullptr;
     m_document = nullptr;
 }
 
-void DocumentWriter::setUserChosenEncoding(const String& charset)
-{
-    TextResourceDecoder* decoder = m_parser->decoder();
-    if (decoder)
-        decoder->setEncoding(charset, TextResourceDecoder::UserChosenEncoding);
-}
-
 void DocumentWriter::setDocumentWasLoadedAsPartOfNavigation()
 {
     ASSERT(m_parser && !m_parser->isStopped());
     m_parser->setDocumentWasLoadedAsPartOfNavigation();
 }
 
 } // namespace blink