Implement HTMLDetailsElement

[KiChjang]

This requires an implementation of the attribute_mutated function in VirtualMethods for HTMLDetailsElement, when attempting to implement the details notification task steps. It also requires the usage of the DOM manipulation task source.

Code: components/script/dom/htmldetailselement.rs (new file), components/script/dom/webidls/HTMLDetailsElement.webidl (new file)
Tests: tests/wpt/web-platform-tests/html/semantics/interactive-elements/the-details-element/details.html
Spec: https://html.spec.whatwg.org/multipage/#htmldetailselement

Requires #9217.

[MonsieurLanza]

This one is appealing me. May I give it a try ?

I understand #9217 is blocking it, but I expect it to be reviewed before I even get rid of

servo/components/script/dom/virtualmethods.rs:20:5: 20:48 error: unresolved import `dom::htmldetailselement::HTMLDetailsElement`. Could not find `htmldetailselement` in `dom` [E0432]

while trying to build.
;)

[jdm]

I think it's possible to work on this without waiting for #9217. Either this work will need to be rebased after it merges, or #9217 will need to be updated to account for this. Either way, I would say go for it :)

[jdm]

As for that error, take a look at components/script/dom/mod.rs :)

[nox]

This module screams "have mercy and codegen the hell out of myself" to me.

[MonsieurLanza]

Thanks. :)

[MonsieurLanza]

The details element should hide non "first-child

" children.

I was wondering how this is supposed to be implemented, and if it is in the scope of the issue ?
My understanding is that could be done in user-agent.css, as this would allow overriding by a user stylesheet. Not sure what to do about this.

Also, user agent should provide a way to toggle the details element, but this is a design decision and goes way beyond just implementing the HTMLDetailsElement interface. ATM, on my working copy, the only way is setting the open attribute via JS.

[jdm]

Yes, we should file a separate issue about exposing a UI for <details>. As for hiding the children, doing that via CSS makes sense to me.