Remove Apple's unused implementation of private browsing from WebCore

Source/WebCore/loader/icon/IconDatabaseBase.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 185 matching lines @@
     virtual size_t retainedPageURLCount() { return 0; }
     virtual size_t iconRecordCount() { return 0; }
     virtual size_t iconRecordCountWithData() { return 0; }
 
     virtual bool shouldStopThreadActivity() const { return true; }
 
     virtual bool open(const String& directory, const String& filename);
     virtual void close() { }
     virtual void removeAllIcons() { }
 
-    virtual void setPrivateBrowsingEnabled(bool) { }
     virtual void setClient(IconDatabaseClient*) { }
     
     virtual bool isOpen() const { return false; }
     virtual String databasePath() const;
 
 };
 
 // Functions to get/set the global icon database.
 IconDatabaseBase& iconDatabase();
 void setGlobalIconDatabase(IconDatabaseBase*);
 bool documentCanHaveIcon(const String&);
 
 } // namespace WebCore
 
 #endif // IconDatabaseBase_h