https://drafts.csswg.org/selectors-4/#zero-matches The Specificity-adjustment pseudo-class, :where(), is a functional pseudo-class with the same syntax and functionality as :is(). Unlike :is(), neither the :where pseudo-class, nor any of its arguments contribute to the specificity of the selector—its specificity is always zero. This is useful for introducing filters in a selector while keeping the associated style declarations easy to override.
Created attachment 396852 [details] patch
Committed r260319: <https://trac.webkit.org/changeset/260319> All reviewed patches have been landed. Closing bug and clearing flags on attachment 396852 [details].
<rdar://problem/61981787>