1 files changed, 21 insertions, 1 deletions
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 39024502b4d..b485cae36de 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -103,6 +103,10 @@ macro_rules! with_all_bounds {
 
             /// pseudo-elements
             type PseudoElement: $($CommonBounds)* + PseudoElement<Impl = Self>;
+
+            /// Returns whether the given pseudo class is :active or :hover.
+            #[inline]
+            fn is_active_or_hover(pseudo_class: &Self::NonTSPseudoClass) -> bool;
         }
     }
 }
@@ -427,7 +431,7 @@ impl<Impl: SelectorImpl> Selector<Impl> {
 
     pub fn iter_from(&self, offset: usize) -> SelectorIter<Impl> {
         // Note: selectors are stored left-to-right but logical order is right-to-left.
-        let iter = self.0.slice[..(self.0.slice.len() - offset)].iter().rev();
+        let iter = self.0.slice[..(self.len() - offset)].iter().rev();
         SelectorIter {
             iter: iter,
             next_combinator: None,
@@ -451,6 +455,11 @@ impl<Impl: SelectorImpl> Selector<Impl> {
         let header = HeaderWithLength::new(SpecificityAndFlags(specificity_and_flags), vec.len());
         Selector(Arc::into_thin(Arc::from_header_and_iter(header, vec.into_iter())))
     }
+
+    /// Returns count of simple selectors and combinators in the Selector.
+    pub fn len(&self) -> usize {
+        self.0.slice.len()
+    }
 }
 
 #[derive(Clone)]
@@ -465,6 +474,11 @@ impl<'a, Impl: 'a + SelectorImpl> SelectorIter<'a, Impl> {
     pub fn next_sequence(&mut self) -> Option<Combinator> {
         self.next_combinator.take()
     }
+
+    /// Returns remaining count of the simple selectors and combinators in the Selector.
+    pub fn selector_length(&self) -> usize {
+        self.iter.len()
+    }
 }
 
 impl<'a, Impl: SelectorImpl> Iterator for SelectorIter<'a, Impl> {
@@ -1711,6 +1725,12 @@ pub mod tests {
         type BorrowedNamespaceUrl = DummyAtom;
         type NonTSPseudoClass = PseudoClass;
         type PseudoElement = PseudoElement;
+
+        #[inline]
+        fn is_active_or_hover(pseudo_class: &Self::NonTSPseudoClass) -> bool {
+            matches!(*pseudo_class, PseudoClass::Active |
+                                    PseudoClass::Hover)
+        }
     }
 
     #[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]