Remove the Document.charset setter (making it readonly)

Source/core/loader/DocumentLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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.
@@ skipping 748 matching lines @@
     return DocumentWriter::create(document.get(), parsingPolicy, mimeType, encoding);
 }
 
 const AtomicString& DocumentLoader::mimeType() const
 {
     if (m_writer)
         return m_writer->mimeType();
     return m_response.mimeType();
 }
 
-void DocumentLoader::setUserChosenEncoding(const String& charset)
-{
-    if (m_writer)
-        m_writer->setUserChosenEncoding(charset);
-}
-
 // This is only called by FrameLoader::replaceDocumentWhileExecutingJavaScriptURL()
 void DocumentLoader::replaceDocumentWhileExecutingJavaScriptURL(const DocumentInit& init, const String& source, Document* ownerDocument)
 {
     m_writer = createWriterFor(ownerDocument, init, mimeType(), m_writer ? m_writer->encoding() : emptyAtom, true, ForceSynchronousParsing);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 } // namespace blink