[cssom] Missing/outdated serialization rules for pseudo-classes #12669
Description
The spec algorithm for serializing pseudo-classes is outdated and missing a lot of newer ones. Specifically it currently lists:
:lang():nth-child(): Missing[of S]?handling:nth-last-child(): Missing[of S]?handling:nth-of-type():nth-last-of-type():not()
And is missing these from level 4:
:dir():is():has():where():nth-col():nth-last-col()
And from level 5:
:state():heading()
As a side note, would it be worth moving the logic for these into the selectors spec and having CSSOM refer to that? I think putting the serialization rules with the pseudo-elements themselves would help keep them up to date, and avoid the issue of which ones should be included in the serialization algorithm.