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

Source/core/html/HTMLElement.cpp

Index: Source/core/html/HTMLElement.cpp
diff --git a/Source/core/html/HTMLElement.cpp b/Source/core/html/HTMLElement.cpp
index 5ca263f1684cdfb0a3dd08ce0c5a7660f097d34c..3c4a002180286d693c1ce30bead60f0da793a58e 100644
--- a/Source/core/html/HTMLElement.cpp
+++ b/Source/core/html/HTMLElement.cpp
@@ -742,6 +742,14 @@ RenderObject* HTMLElement::createRenderer(RenderStyle* style)
     return RenderObject::createObject(this, style);
 }
 
+HTMLFormElement* HTMLElement::formOwner() const

[tkent, 2013/12/10 23:19:28]

This function always calls a virtual function isFormAssociatedElement(), and
calls another virtual function virtualForm() if this is
isFormAssociatedElement(). It's inefficient.

Why don't you just make formOwner() virtual, and override it in form-associated
elements?

Unfortunately we already have FormAssociatedElement class and
isFormAssociatedElement() doesn't match to it. It's very confusing.

[sof, 2013/12/11 07:55:03]

Agreed, too much indirection here.

As suggested, I've virtualized formOwner() instead, doing away with the explicit
is-form-associated predicate. Looks better?

(The reason there isn't an exact overlap with FormAssociatedElement and the
form-associated predicate in the spec is <label> and <img>.)

+{
+    if (!isFormAssociatedElement())
+        return 0;
+
+    return virtualForm();
+}
+
 HTMLFormElement* HTMLElement::findFormAncestor() const
 {
     for (ContainerNode* ancestor = parentNode(); ancestor; ancestor = ancestor->parentNode()) {