Fix virtual/override/final usage in Source/core/{fetch,loader,streams,xmlhttprequest}/.

Source/core/xmlhttprequest/XMLHttpRequestProgressEvent.h

 /*
  * Copyright (C) 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Julien Chaffraix <jchaffraix@webkit.org>. 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 33 matching lines @@
     }
     static PassRefPtrWillBeRawPtr<XMLHttpRequestProgressEvent> create(const AtomicString& type, bool lengthComputable = false, unsigned long long loaded = 0, unsigned long long total = 0)
     {
         return adoptRefWillBeNoop(new XMLHttpRequestProgressEvent(type, lengthComputable, loaded, total));
     }
 
     // Those 2 synonyms are included for compatibility with Firefox.
     unsigned long long position() const { return loaded(); }
     unsigned long long totalSize() const { return total(); }
 
-    virtual const AtomicString& interfaceName() const override { return EventNames::XMLHttpRequestProgressEvent; }
+    const AtomicString& interfaceName() const override { return EventNames::XMLHttpRequestProgressEvent; }
 
     DEFINE_INLINE_VIRTUAL_TRACE() { ProgressEvent::trace(visitor); }
 
 private:
     XMLHttpRequestProgressEvent() { }
 
     XMLHttpRequestProgressEvent(const AtomicString& type, bool lengthComputable, unsigned long long loaded, unsigned long long total)
         : ProgressEvent(type, lengthComputable, loaded, total) { }
 };
 
 } // namespace blink
 
 #endif // XMLHttpRequestProgressEvent_h