Intent to prototype and ship: accent-color CSS property

[Emilio Cobos Álvarez]

Summary: the accent-color CSS property allows authors to customize the
accent color used for native form controls (such as checkbox
backgrounds, border colors, etc).

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1722031

Standard: https://drafts.csswg.org/css-ui-4/#widget-accent

Platform coverage: all

Preference: layout.css.accent-color.enabled

DevTools bug: N/A

Other browsers:

* WebKit: Not implemented yet.
* Blink: Should be shipping soon per
https://groups.google.com/a/chromium.org/g/blink-dev/c/WwYkLjbGhoA/m/_u36s04MAgAJ

web-platform-tests: Native form rendering of form controls is hard to
test in WPT because they're per definition browser or even platform
specific. There are some tests in here for the testable bits though:


https://wpt.fyi/results/css/css-ui?label=master&label=experimental&aligned&q=accent-color

Cheers,

-- Emilio