[cssom] Should getComputedStyle() support non-standard pseudo-elements? #3980
Description
https://drafts.csswg.org/cssom/#dom-window-getcomputedstyle
See #3968 (comment)
Why does getComputedStyle() support any pseudo-element? Previously it only supported ::before and ::after.
This is an issue for appearance because UAs can support non-standard values for non-standard pseudo-elements. (Though css-ui could require auto to be used instead.)
Do we want such pseudo-elements to be available in author CSS? Do we want to support them in getComputedStyle()?