1 files changed, 8 insertions, 0 deletions
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 507121bbf97..92a5b039b90 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -52,6 +52,9 @@ pub trait NonTSPseudoClass: Sized + ToCss {
     ///
     /// https://drafts.csswg.org/selectors-4/#useraction-pseudos
     fn is_user_action_state(&self) -> bool;
+
+    /// Whether this pseudo-class has zero specificity.
+    fn has_zero_specificity(&self) -> bool;
 }
 
 /// Returns a Cow::Borrowed if `s` is already ASCII lowercase, and a
@@ -2336,6 +2339,11 @@ pub mod tests {
         fn is_user_action_state(&self) -> bool {
             self.is_active_or_hover()
         }
+
+        #[inline]
+        fn has_zero_specificity(&self) -> bool {
+            false
+        }
     }
 
     impl ToCss for PseudoClass {