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

Source/core/html/HTMLFormControlElement.cpp

Index: Source/core/html/HTMLFormControlElement.cpp
diff --git a/Source/core/html/HTMLFormControlElement.cpp b/Source/core/html/HTMLFormControlElement.cpp
index 4e361a6f200ddd4689c69973003bc5fa8437299f..4c68907eaf4d994dd4f341fe69ce0400450f88f2 100644
--- a/Source/core/html/HTMLFormControlElement.cpp
+++ b/Source/core/html/HTMLFormControlElement.cpp
@@ -297,6 +297,11 @@ void HTMLFormControlElement::dispatchFormControlInputEvent()
     HTMLElement::dispatchInputEvent();
 }
 
+HTMLFormElement* HTMLFormControlElement::formOwner() const
+{
+    return FormAssociatedElement::form();
+}
+
 bool HTMLFormControlElement::isDisabledFormControl() const
 {
     if (m_disabled)
@@ -498,11 +503,6 @@ void HTMLFormControlElement::dispatchBlurEvent(Element* newFocusedElement)
     hideVisibleValidationMessage();
 }
 
-HTMLFormElement* HTMLFormControlElement::virtualForm() const
-{
-    return FormAssociatedElement::form();
-}
-
 bool HTMLFormControlElement::isSuccessfulSubmitButton() const
 {
     return canBeSuccessfulSubmitButton() && !isDisabledFormControl();