The 'strict' and 'content' keywords for the 'contain' property will now include 'style'. Per CSSWG resolution this was (re-)added now that contain:style is well-defined in the specifications.
A previous intent (*) removed contain: style from these keywords, since contain:style was not well-enough specified to obtain spec consensus. Subsequently, the spec issues were fixed and consensus was achieved (**), so contain:style is now being re-added. (*) https://groups.google.com/a/chromium.org/g/blink-dev/c/fKtqaykk4Bs/m/SOAvgeOyCwAJ (**) https://github.com/w3c/csswg-drafts/issues/6287#issuecomment-862525199