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

Source/core/dom/ChildNodeList.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 21 matching lines @@
 
 namespace blink {
 
 class ChildNodeList final : public NodeList {
 public:
     static PassRefPtrWillBeRawPtr<ChildNodeList> create(ContainerNode& rootNode)
     {
         return adoptRefWillBeNoop(new ChildNodeList(rootNode));
     }
 
-    virtual ~ChildNodeList();
+    ~ChildNodeList() override;
 
     // DOM API.
-    virtual unsigned length() const override { return m_collectionIndexCache.nodeCount(*this); }
-    virtual Node* item(unsigned index) const override { return m_collectionIndexCache.nodeAt(*this, index); }
+    unsigned length() const override { return m_collectionIndexCache.nodeCount(*this); }
+    Node* item(unsigned index) const override { return m_collectionIndexCache.nodeAt(*this, index); }
 
     // Non-DOM API.
     void invalidateCache() { m_collectionIndexCache.invalidate(); }
     ContainerNode& ownerNode() const { return *m_parent; }
 
     ContainerNode& rootNode() const { return ownerNode(); }
 
     // CollectionIndexCache API.
     bool canTraverseBackward() const { return true; }
     Node* traverseToFirst() const { return rootNode().firstChild(); }
     Node* traverseToLast() const { return rootNode().lastChild(); }
     Node* traverseForwardToOffset(unsigned offset, Node& currentNode, unsigned& currentOffset) const;
     Node* traverseBackwardToOffset(unsigned offset, Node& currentNode, unsigned& currentOffset) const;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit ChildNodeList(ContainerNode& rootNode);
 
-    virtual bool isChildNodeList() const override { return true; }
-    virtual Node* virtualOwnerNode() const override;
+    bool isChildNodeList() const override { return true; }
+    Node* virtualOwnerNode() const override;
 
     RefPtrWillBeMember<ContainerNode> m_parent;
     mutable CollectionIndexCache<ChildNodeList, Node> m_collectionIndexCache;
 };
 
 DEFINE_TYPE_CASTS(ChildNodeList, NodeList, nodeList, nodeList->isChildNodeList(), nodeList.isChildNodeList());
 
 } // namespace blink
 
 #endif // ChildNodeList_h