Remove support of field-sizing from `<select>`

[sakupi01]

What is the issue with the HTML Standard?

As resolved in w3c/csswg-drafts#11879, <select> will no longer be an element with default preferred size, and the field-sizing: content !important; is going to be added to the new select UA stylesheet spec.

• Add UA stylesheet for <select> base appearance #10670

For this reason, it's reasonable to update the existing HTML spec.
e.g. the following and other related parts should be removed&updated:

The select element is an element with default preferred size, and user agents are expected to apply the 'field-sizing' CSS property to select elements.
https://html.spec.whatwg.org/multipage/rendering.html#the-select-element-2

Although speccing the new <select>'s UA stylesheet is under construction, I'd love to PR for the default preferred size part!

Filed an issue in CSS: w3c/csswg-drafts#12055

[annevk]

cc @josepharhar @nt1m

[josepharhar]

This only applies when the select has base appearance. With native/primitive appearance, field-sizing is still supported.

[sakupi01]

@josepharhar
Indeed. This change applies specifically to <select> with base appearance, while <select> with native/primitive appearance will continue to support field-sizing and remain an element with default preferred size.

Given this distinction, I suspect it'd it be more appropriate to update the spec to clarify rather than completely remove the text. Something like:

The select element with native/primitive appearance is an element with default preferred size, and user agents are expected to apply the 'field-sizing' CSS property to such select elements. However, select elements with base appearance have field-sizing: content !important applied in their UA stylesheet.

While the above example should be refined enough, it's worthwhile to add a clarification note to maintain consistency with the CSS spec while also reflecting the new behaviour for <select> with base appearance.

[lukewarlow]

I don't think this actually needs any edits at all? User agents do apply that property to select, they just happen to force it to content in base appearance mode (this important modifier might be lifted in future if it's desirable).

Though I guess it can't hurt to clarify this (especially as I think it's intended that HTML will own the UA stylesheet).