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

Source/core/html/HTMLFormControlElement.cpp

 /*
  * 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, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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 279 matching lines @@
     HTMLElement::dispatchChangeEvent();
     setChangedSinceLastFormControlChangeEvent(false);
 }
 
 void HTMLFormControlElement::dispatchFormControlInputEvent()
 {
     setChangedSinceLastFormControlChangeEvent(true);
     HTMLElement::dispatchInputEvent();
 }
 
+HTMLFormElement* HTMLFormControlElement::formOwner() const
+{
+    return FormAssociatedElement::form();
+}
+
 bool HTMLFormControlElement::isDisabledFormControl() const
 {
     if (m_disabled)
         return true;
 
     if (m_ancestorDisabledState == AncestorDisabledStateUnknown)
         updateAncestorDisabledState();
     return m_ancestorDisabledState == AncestorDisabledStateDisabled;
 }
 
@@ skipping 181 matching lines @@
     FormAssociatedElement::setCustomValidity(error);
     setNeedsValidityCheck();
 }
 
 void HTMLFormControlElement::dispatchBlurEvent(Element* newFocusedElement)
 {
     HTMLElement::dispatchBlurEvent(newFocusedElement);
     hideVisibleValidationMessage();
 }
 
-HTMLFormElement* HTMLFormControlElement::virtualForm() const
-{
-    return FormAssociatedElement::form();
-}
-
 bool HTMLFormControlElement::isSuccessfulSubmitButton() const
 {
     return canBeSuccessfulSubmitButton() && !isDisabledFormControl();
 }
 
 bool HTMLFormControlElement::isDefaultButtonForForm() const
 {
     return isSuccessfulSubmitButton() && form() && form()->defaultButton() == this;
 }
 
@@ skipping 11 matching lines @@
     String fullName = name();
     String trimmedName = fullName.stripWhiteSpace();
     if (!trimmedName.isEmpty())
         return trimmedName;
     fullName = getIdAttribute();
     trimmedName = fullName.stripWhiteSpace();
     return trimmedName;
 }
 
 } // namespace Webcore