Bug 118007 – Introduce toHTMLFormControlElement and use it

• Status: RESOLVED
• Resolution: WONTFIX
• Component: Forms

[Ryosuke Niwa]

https://chromium.googlesource.com/chromium/blink/+/6808b29390234652e9a3b30fe2bba67b83247134

Note for 'alias'-related changes in HTMLFormElement:
We had unnecessary cast from Node to HTMLFormControlElement.
m_elementAliases can contain HTMLImageElement and HTMLObjectElement
in addition to HTMLFormControlElement. A node was cast to
HTMLFormControlElement wrongly, but it was harmless because nodes
stored in m_elementAliases are used as Node*.


Note for the HTMLSelectElement.h change:
HTMLKeyGenElement::reset() wants to call HTMLSelectElement::reset(), and
it was realized by a cast to HTMLFormControlElement, of which reset() is
public. Replacing the cast to toHTMLFormControlElement doesn't work
because both of toHTMLFormControlElement(Node*) and
toHTMLFormControlElement(FormAssociatedElement*) match to an
HTMLSelectElement argument.
The public reset() makes the code simpler.

[Ryosuke Niwa]

We have downcast<HTMLFormControlElement> now.