Help with CSS Parser to recognize :where(.class) styles

[glaprida]

For specificity reasons, I need to set some styles to the :where(.class) selector instead of just doing .class (the reason being :where has a specificity score of 0,0,0 while .class has 0,1,0 )

The problem is those styles are not being recognized in the styleManager. As far as I understand, this could be done by extending the CSSparser; but after some failed tries I came here seeking help.

Am I looking at this the right way? or is there a better approach?
Anyone know how to extend the CSS parser to recongnize those styles?

Thanks!