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

Source/core/dom/ChildNodeList.h

Index: Source/core/dom/ChildNodeList.h
diff --git a/Source/core/dom/ChildNodeList.h b/Source/core/dom/ChildNodeList.h
index 4a126f5dd66c349f1a7b1a15bbfa01ad0b855bdf..ddeda6b063f49cdf5663544615f3267c6b53d842 100644
--- a/Source/core/dom/ChildNodeList.h
+++ b/Source/core/dom/ChildNodeList.h
@@ -39,11 +39,11 @@ public:
         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(); }
@@ -63,8 +63,8 @@ public:
 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;