[css-values] define parse-time value aliasing

[emilio]

This is a thing which, just as property and selector aliases, exist. The later two are well defined, so we need to define this too.

Some examples in Firefox: https://searchfox.org/mozilla-central/search?q=parse%28alias&path=&case=false&regexp=false

[fantasai]

Agenda+ to review the new section: https://drafts.csswg.org/css-cascade-4/#value-aliasing

[css-meeting-bot]

The CSS Working Group just discussed [css-values] define parse-time value aliasing, and agreed to the following:

• RESOLVED: Accept edits, expand to allow aliased functions

The full IRC log of that discussion

<fantasai> Topic: [css-values] define parse-time value aliasing
<chris> miriam: is the changes section up to date?
<fantasai> github: https://github.com//issues/6193
<emilio> scribenick: emilio
<fantasai> fantasai: Added value aliasing section to cascade-4/5
<fantasai> emilio: Weird that it is scoped to keywords
<fantasai> fantasai: We didn't see any examples of not keywords, but could certainly reword to be more general
<emilio> emilio `-webkit-image-set()`-> `image-set()`
<emilio> Same with a bunch of gradient functions
<chris_> rrsagent, here
<RRSAgent> See https://un5gmtkzgkj46tygt32g.julianrbryant.com/2021/11/17-css-irc#T17-27-14
<fantasai> fantasai: So functions and keywords, anything else?
<fantasai> s/scribenick: emilio//
<emilio> I don't _think_ so of the top of my head
<fantasai> astearns: So proposed to take edits, with additional change to add functions
<fantasai> fantasai: sgtm
<emilio> emilio: sgtm
<fantasai> RESOLVED: Accept edits, expand to allow aliased functions