1 files changed, 24 insertions, 0 deletions
diff --git a/servo/components/style/invalidation/element/element_wrapper.rs b/servo/components/style/invalidation/element/element_wrapper.rs
index e17afd7774..9a39b7d5a0 100644
--- a/servo/components/style/invalidation/element/element_wrapper.rs
+++ b/servo/components/style/invalidation/element/element_wrapper.rs
@@ -73,6 +73,18 @@ pub trait ElementSnapshot: Sized {
     where
         F: FnMut(&AtomIdent);
 
+
+    /// If this snapshot contains CustomStateSet information.
+    fn has_custom_states(&self) -> bool;
+
+    /// A callback that should be called for each CustomState of the snapshot.
+    fn has_custom_state(&self, state: &AtomIdent) -> bool;
+
+    /// A callback that should be called for each CustomState of the snapshot.
+    fn each_custom_state<F>(&self, callback: F)
+    where
+        F: FnMut(&AtomIdent);
+
     /// The `xml:lang=""` or `lang=""` attribute value per this snapshot.
     fn lang_attr(&self) -> Option<AttrValue>;
 }
@@ -213,6 +225,11 @@ where
                     .match_element_lang(Some(self.get_lang()), lang_arg);
             },
 
+            // CustomStateSet should match against the snapshot before element
+            NonTSPseudoClass::CustomState(ref state) => {
+                return self.has_custom_state(&state.0)
+            },
+
             _ => {},
         }
 
@@ -357,6 +374,13 @@ where
         }
     }
 
+    fn has_custom_state(&self, state: &AtomIdent) -> bool {
+        match self.snapshot() {
+            Some(snapshot) if snapshot.has_custom_states() => snapshot.has_custom_state(state),
+            _ => self.element.has_custom_state(state),
+        }
+    }
+
     fn is_empty(&self) -> bool {
         self.element.is_empty()
     }