Function element_is_outside_of_scope 

pub fn element_is_outside_of_scope<E>(
    selector: &Selector<E::Impl>,
    element: E,
    root: OpaqueElement,
    context: &mut MatchingContext<'_, E::Impl>,
    root_may_be_shadow_host: bool,
) -> bool
where
    E: TElement,

Given the scope-end selector, check if the element is outside of the scope. That is, check if any ancestor to the root matches the scope-end selector.