[csswg-drafts] [css-contain] Is it ok that contain:layout is a CB for fixpos/abspos descendants but doesn't establish a stacking context?

dbaron has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-contain] Is it ok that contain:layout is a CB for fixpos/abspos descendants but doesn't establish a stacking context? ==
[The containment spec for `contain:layout`](https://drafts.csswg.org/css-contain/#containment-layout):
* says that `contain:layout` establishes a containing block for absolutely positioned and fixed positioned descendants, but
* does not say that it establishes a stacking context.

This is the first feature in CSS that I'm aware of with this combination.  I think it's worth some consideration of whether this combination is sensible.  Do the painting rules for abspos and fixpos elements contained by such an element work in a reasonable way?

/cc @MReschenberg

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2942 using your GitHub account