Implement HTMLFormElement.relList

[jdm]

Spec:

• https://html.spec.whatwg.org/#the-form-element:dom-form-rellist
• https://html.spec.whatwg.org/#dom-form-rellist

This can be implemented by duplicating the implementation of HTMLAnchorElement as well as adding the missing IDL to components/script/dom/webidls/HTMLFormElement.webidl.

Tests: ./mach test-wpt tests/wpt/web-platform-tests/html/dom/idlharness.https.html
We will need to update tests/wpt/metadata/html/dom/idlharness.https.html.ini to remove the expected failures that will now pass after this change.

[highfive]

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[avr1254]

When I copy the implementation from HTMLAnchorElement, I get an error about self.rel_list being an unknown field. Sorry for the newb question, but should I add a rel_list to the HTMLFromElement struct?

[jdm]

Yes, add the rel_list to HTMLFormElement like the one in HTMLAnchorElement.

It also looks like we're missing HTMLFormElement.rel as well (https://html.spec.whatwg.org/multipage/forms.html#the-form-element:dom-form-rel). It should be possible to duplicate the implementation of that from HTMLAnchorElement, too, but there are a couple pieces:

• parse_plain_attribute
• the getter and setter

[avr1254]

Thanks! I'll take a look.