Function matched_rules_for 

pub fn matched_rules_for(
    subject: &AncestorInfo,
    css: &Stylesheet,
    media: &MediaContext,
    ancestors: &[AncestorInfo],
    has_element_children: bool,
    text_body: Option<&str>,
) -> Vec<MatchedRuleInfo>

Rules that match subject given its ancestors (root-first), with cascade provenance, ascending in cascade order (last wins). Reuses the cascade matcher’s own collect_matching_rules, so this is the same match set the restyle pass resolves; no second selector engine. An inspection call backing matched_rules().