Fix virtual/override/final usage in Source/core/dom/.

Source/core/dom/EmptyNodeList.h

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 25 matching lines @@
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class EmptyNodeList final : public NodeList {
 public:
     static PassRefPtrWillBeRawPtr<EmptyNodeList> create(Node& rootNode)
     {
         return adoptRefWillBeNoop(new EmptyNodeList(rootNode));
     }
-    virtual ~EmptyNodeList();
+    ~EmptyNodeList() override;
 
     Node& ownerNode() const { return *m_owner; }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit EmptyNodeList(Node& rootNode) : m_owner(rootNode) { }
 
-    virtual unsigned length() const override { return 0; }
-    virtual Node* item(unsigned) const override { return 0; }
+    unsigned length() const override { return 0; }
+    Node* item(unsigned) const override { return 0; }
 
-    virtual bool isEmptyNodeList() const override { return true; }
-    virtual Node* virtualOwnerNode() const override;
+    bool isEmptyNodeList() const override { return true; }
+    Node* virtualOwnerNode() const override;
 
     RefPtrWillBeMember<Node> m_owner;
 };
 
 DEFINE_TYPE_CASTS(EmptyNodeList, NodeList, nodeList, nodeList->isEmptyNodeList(), nodeList.isEmptyNodeList());
 
 } // namespace blink
 
 #endif // EmptyNodeList_h