style: Don't use rule cache for property-restricted pseudo-elements.

components/style/properties/properties.mako.rs

@@ -2600,7 +2600,7 @@ pub struct StyleBuilder<'a> {
     custom_properties: Option<Arc<::custom_properties::CustomPropertiesMap>>,
 
     /// The pseudo-element this style will represent.
-    pseudo: Option<<&'a PseudoElement>,
+    pub pseudo: Option<<&'a PseudoElement>,
 
     /// Whether we have mutated any reset structs since the the last time
     /// `clear_modified_reset` was called.  This is used to tell whether the

components/style/rule_cache.rs

@@ -9,6 +9,7 @@ use fnv::FnvHashMap;
 use logical_geometry::WritingMode;
 use properties::{ComputedValues, StyleBuilder};
 use rule_tree::StrongRuleNode;
+use selector_parser::PseudoElement;
 use servo_arc::Arc;
 use smallvec::SmallVec;
 use values::computed::NonNegativeLength;
@@ -93,6 +94,14 @@ impl RuleCache {
             return None;
         }
 
+        // A pseudo-element with property restrictions can result in different
+        // computed values if it's also used for a non-pseudo.
+        if builder_with_early_props.pseudo
+           .and_then(|p| p.property_restriction())
+           .is_some() {
+            return None;
+        }
+
         let rules = match builder_with_early_props.rules {
             Some(ref rules) => rules,
             None => return None,
@@ -115,6 +124,7 @@ impl RuleCache {
     pub fn insert_if_possible(
         &mut self,
         style: &Arc<ComputedValues>,
+        pseudo: Option<&PseudoElement>,
         conditions: &RuleCacheConditions,
     ) -> bool {
         if !conditions.cacheable() {
@@ -126,6 +136,12 @@ impl RuleCache {
             return false;
         }
 
+        // A pseudo-element with property restrictions can result in different
+        // computed values if it's also used for a non-pseudo.
+        if pseudo.and_then(|p| p.property_restriction()).is_some() {
+            return false;
+        }
+
         let rules = match style.rules {
             Some(ref r) => r.clone(),
             None => return false,

components/style/style_resolver.rs

@@ -574,11 +574,13 @@ where
         }
 
         let implemented_pseudo = self.element.implemented_pseudo_element();
+        let pseudo = pseudo.or(implemented_pseudo.as_ref());
+
         let mut conditions = Default::default();
         let values =
             cascade(
                 self.context.shared.stylist.device(),
-                pseudo.or(implemented_pseudo.as_ref()),
+                pseudo,
                 rules.unwrap_or(self.context.shared.stylist.rule_tree().root()),
                 &self.context.shared.guards,
                 parent_style,
@@ -595,7 +597,7 @@ where
         self.context
             .thread_local
             .rule_cache
-            .insert_if_possible(&values, &conditions);
+            .insert_if_possible(&values, pseudo, &conditions);
 
         values
     }