Have ElementTraversal / NodeTraversal's next() methods take a reference

Source/core/html/FormAssociatedElement.cpp

Index: Source/core/html/FormAssociatedElement.cpp
diff --git a/Source/core/html/FormAssociatedElement.cpp b/Source/core/html/FormAssociatedElement.cpp
index b1de0fc340b79633827c8d849734a7ede886a543..5b45b8bf06bb7f9d75b7d3eaf0bad9b69397dc06 100644
--- a/Source/core/html/FormAssociatedElement.cpp
+++ b/Source/core/html/FormAssociatedElement.cpp
@@ -135,7 +135,7 @@ void FormAssociatedElement::setForm(HTMLFormElement* newForm)
         m_form->removeFormElement(this);
     m_form = newForm;
     if (m_form)
-        m_form->registerFormElement(this);
+        m_form->registerFormElement(*this);
     didChangeForm();
 }
 
@@ -274,19 +274,30 @@ bool FormAssociatedElement::isFormControlElementWithState() const
     return false;
 }
 
-const HTMLElement* toHTMLElement(const FormAssociatedElement* associatedElement)
+const HTMLElement& toHTMLElement(const FormAssociatedElement& associatedElement)
 {
-    if (associatedElement->isFormControlElement())
+    if (associatedElement.isFormControlElement())
         return toHTMLFormControlElement(associatedElement);
     // Assumes the element is an HTMLObjectElement
     return toHTMLObjectElement(associatedElement);
 }
 
+const HTMLElement* toHTMLElement(const FormAssociatedElement* associatedElement)
+{
+    ASSERT(associatedElement);
+    return &toHTMLElement(*associatedElement);
+}
+
 HTMLElement* toHTMLElement(FormAssociatedElement* associatedElement)
 {
     return const_cast<HTMLElement*>(toHTMLElement(static_cast<const FormAssociatedElement*>(associatedElement)));
 }
 
+HTMLElement& toHTMLElement(FormAssociatedElement& associatedElement)
+{
+    return const_cast<HTMLElement&>(toHTMLElement(static_cast<const FormAssociatedElement&>(associatedElement)));
+}
+
 PassOwnPtr<FormAttributeTargetObserver> FormAttributeTargetObserver::create(const AtomicString& id, FormAssociatedElement* element)
 {
     return adoptPtr(new FormAttributeTargetObserver(id, element));