Auto merge of #16875 - bzbarsky:dir-no-revalidation, r=emilio

Don't require style sharing cache invalidation for :dir

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components/style/gecko/selector_parser.rs

@@ -159,8 +159,12 @@ impl NonTSPseudoClass {
 
     /// Returns true if the given pseudoclass should trigger style sharing cache revalidation.
     pub fn needs_cache_revalidation(&self) -> bool {
+        // :dir() depends on state only, but doesn't use state_flag because its
+        // semantics don't quite match.  Nevertheless, it doesn't need cache
+        // revalidation, because we already compare states for elements and
+        // candidates.
         self.state_flag().is_empty() &&
-        !matches!(*self, NonTSPseudoClass::MozAny(_))
+        !matches!(*self, NonTSPseudoClass::MozAny(_) | NonTSPseudoClass::Dir(_))
     }
 
     /// Convert NonTSPseudoClass to Gecko's CSSPseudoClassType.