Intent to prototype: :has-slotted pseudo

[Keith Cirkel]

Summary:

  The :has-slotted pseudo class represents a slot element with slotted content, such as a text node or element. This can be used to style elements based on whether or not they are using slot fallback content.

I intend to prototype this out in Gecko.

Bug:

  https://bugzilla.mozilla.org/show_bug.cgi?id=1921747.

Specification:

  https://drafts.csswg.org/css-scoping/#the-has-slotted-pseudo

Standards Body:

  CSSWG

Platform coverage:

  all.

Preference:

  dom.has_slotted.enabled

DevTools bug:

 n/a.

Link to standards-positions discussion:

  https://github.com/mozilla/standards-positions/issues/1079.

Other browsers:

  Blink: Prototyping.

  WebKit: No Signals (https://github.com/WebKit/standards-positions/issues/404).

web-platform-tests:

  https://wpt.fyi/results/css/css-scoping?label=experimental&label=master&aligned