Remove the Document.charset setter (making it readonly)

Source/core/loader/DocumentLoader.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 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 58 matching lines @@
         LocalFrame* frame() const { return m_frame; }
 
         void detachFromFrame();
 
         unsigned long mainResourceIdentifier() const;
 
         void replaceDocumentWhileExecutingJavaScriptURL(const DocumentInit&, const String& source, Document*);
 
         const AtomicString& mimeType() const;
 
-        void setUserChosenEncoding(const String& charset);
-
         const ResourceRequest& originalRequest() const;
 
         const ResourceRequest& request() const;
 
         ResourceFetcher* fetcher() const { return m_fetcher.get(); }
 
         const SubstituteData& substituteData() const { return m_substituteData; }
 
         const KURL& url() const;
         const KURL& unreachableURL() const;
@@ skipping 127 matching lines @@
         friend class ApplicationCacheHost;  // for substitute resource delivery
         OwnPtrWillBePersistent<ApplicationCacheHost> m_applicationCacheHost;
 
         RefPtr<ContentSecurityPolicy> m_contentSecurityPolicy;
         ClientHintsPreferences m_clientHintsPreferences;
         InitialScrollState m_initialScrollState;
     };
 }
 
 #endif // DocumentLoader_h