The :scope pseudo-class inside :has(), :is(), :where(), and :not()
selectors was not receiving the scoping root from outer selector
contexts like Element.closest().
This fix passes the scope parameter through matches_has_pseudo_class(),
matches_relative_selector(), and the :is()/:where()/:not() cases so
that :scope correctly refers to the scoping root element.
This fixes WPT tests for Element.closest() with selector
':has(> :scope)' and for comparing :has(:scope) with :is(:scope)
selectors.
