Clean up virtual function in Source/html

Source/core/html/HTMLUnknownElement.h

Index: Source/core/html/HTMLUnknownElement.h
diff --git a/Source/core/html/HTMLUnknownElement.h b/Source/core/html/HTMLUnknownElement.h
index 9d400bfb9ee786a2a37f575b5116ce439df77c3f..064e573fd3bbaff96b9763c21fd17393203f79f7 100644
--- a/Source/core/html/HTMLUnknownElement.h
+++ b/Source/core/html/HTMLUnknownElement.h
@@ -42,11 +42,11 @@ public:
         return adoptRefWillBeNoop(new HTMLUnknownElement(tagName, document));
     }
 
-    virtual bool isHTMLUnknownElement() const override { return true; }
-
 private:
     HTMLUnknownElement(const QualifiedName& tagName, Document& document)
         : HTMLElement(tagName, document) { }
+
+    virtual bool isHTMLUnknownElement() const override { return true; }
 };
 
 inline bool isHTMLUnknownElement(const HTMLElement& element)