Only 'form associated' elements have a potential form owner.

Source/core/html/HTMLElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Motorola Mobility. 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 662 matching lines @@
 
 HTMLFormElement* HTMLElement::findFormAncestor() const
 {
     for (ContainerNode* ancestor = parentNode(); ancestor; ancestor = ancestor->parentNode()) {
         if (ancestor->hasTagName(formTag))
             return toHTMLFormElement(ancestor);
     }
     return 0;
 }
 
-HTMLFormElement* HTMLElement::virtualForm() const
-{
-    return findFormAncestor();
-}
-
 static inline bool elementAffectsDirectionality(const Node* node)
 {
     return node->isHTMLElement() && (node->hasTagName(bdiTag) || toHTMLElement(node)->hasAttribute(dirAttr));
 }
 
 static void setHasDirAutoFlagRecursively(Node* firstNode, bool flag, Node* lastNode = 0)
 {
     firstNode->setSelfOrAncestorHasDirAutoAttribute(flag);
 
     Node* node = firstNode->firstChild();
@@ skipping 306 matching lines @@
 #ifndef NDEBUG
 
 // For use in the debugger
 void dumpInnerHTML(WebCore::HTMLElement*);
 
 void dumpInnerHTML(WebCore::HTMLElement* element)
 {
     printf("%s\n", element->innerHTML().ascii().data());
 }
 #endif