[css-pseudo] Allow custom Properties in ::selection pseudos (revisited)

[chromium-helper]

CSSWG added the following resolution(s):

• RESOLVED: allow custom properties on highlight pseudos
• RESOLVED: Allow custom properties on highlight pseudoes; custom properties continue to inherit from the originating element

in w3c/csswg-drafts#11317 (comment)

[chromium-helper]

I have filed issues.chromium.org/393180640

That is all that can be done here, closing issue.