Fix virtual/override/final usage in the rest of Source/core/.

Source/core/events/RelatedEvent.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RelatedEvent_h
 #define RelatedEvent_h
 
 #include "core/events/Event.h"
 #include "core/events/RelatedEventInit.h"
 
 namespace blink {
 
 class RelatedEvent final : public Event {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<RelatedEvent> create();
     static PassRefPtrWillBeRawPtr<RelatedEvent> create(const AtomicString& type, bool canBubble, bool cancelable, EventTarget* relatedTarget);
     static PassRefPtrWillBeRawPtr<RelatedEvent> create(const AtomicString& eventType, const RelatedEventInit&);
 
-    virtual ~RelatedEvent();
+    ~RelatedEvent() override;
 
     EventTarget* relatedTarget() const { return m_relatedTarget.get(); }
 
-    virtual const AtomicString& interfaceName() const override { return EventNames::RelatedEvent; }
-    virtual bool isRelatedEvent() const override { return true; }
+    const AtomicString& interfaceName() const override { return EventNames::RelatedEvent; }
+    bool isRelatedEvent() const override { return true; }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     RelatedEvent();
     RelatedEvent(const AtomicString& type, bool canBubble, bool cancelable, EventTarget*);
     RelatedEvent(const AtomicString& type, const RelatedEventInit&);
 
     RefPtrWillBeMember<EventTarget> m_relatedTarget;
 };
 
 DEFINE_EVENT_TYPE_CASTS(RelatedEvent);
 
 } // namespace blink
 
 #endif // RelatedEvent_h