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

Source/core/html/HTMLElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009 Apple Inc. 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 59 matching lines @@
 
     void click();
 
     virtual void accessKeyAction(bool sendMouseEvents);
 
     bool ieForbidsInsertHTML() const;
 
     virtual bool rendererIsNeeded(const RenderStyle&);
     virtual RenderObject* createRenderer(RenderStyle*);
 
-    HTMLFormElement* formOwner() const { return virtualForm(); }
+    virtual HTMLFormElement* formOwner() const { return 0; }
 
     HTMLFormElement* findFormAncestor() const;
 
     bool hasDirectionAuto() const;
     TextDirection directionalityIfhasDirAutoAttribute(bool& isAuto) const;
 
     virtual bool isHTMLUnknownElement() const { return false; }
 
     virtual bool isLabelable() const { return false; }
     // http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#interactive-content
@@ skipping 15 matching lines @@
     unsigned parseBorderWidthAttribute(const AtomicString&) const;
 
     virtual void childrenChanged(bool changedByParser = false, Node* beforeChange = 0, Node* afterChange = 0, int childCountDelta = 0);
     void calculateAndAdjustDirectionality();
 
 private:
     virtual String nodeName() const OVERRIDE FINAL;
 
     void mapLanguageAttributeToLocale(const AtomicString&, MutableStylePropertySet*);
 
-    virtual HTMLFormElement* virtualForm() const;
-
     PassRefPtr<DocumentFragment> textToFragment(const String&, ExceptionState&);
 
     void dirAttributeChanged(const AtomicString&);
     void adjustDirectionalityIfNeededAfterChildAttributeChanged(Element* child);
     void adjustDirectionalityIfNeededAfterChildrenChanged(Node* beforeChange, int childCountDelta);
     TextDirection directionality(Node** strongDirectionalityTextNode= 0) const;
 
     TranslateAttributeMode translateAttributeMode() const;
 
     const AtomicString& eventNameForAttributeName(const QualifiedName& attrName) const;
 
     void handleKeypressEvent(KeyboardEvent*);
     bool supportsSpatialNavigationFocus() const;
 };
 
 DEFINE_NODE_TYPE_CASTS(HTMLElement, isHTMLElement());
 
 inline HTMLElement::HTMLElement(const QualifiedName& tagName, Document& document, ConstructionType type = CreateHTMLElement)
     : Element(tagName, &document, type)
 {
     ASSERT(!tagName.localName().isNull());
     ScriptWrappable::init(this);
 }
 
 } // namespace WebCore
 
 #endif // HTMLElement_h