Auto merge of #16090 - bzbarsky:required-optional, r=emilio

Implement :required/:optional support for stylo.

Servo side of https://bugzilla.mozilla.org/show_bug.cgi?id=1349659

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- [ ] These changes fix #__ (github issue number if applicable).

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components/style/element_state.rs

@@ -57,7 +57,11 @@ bitflags! {
         const IN_HANDLER_DISABLED_STATE = 1 << 18,
         #[doc = "Non-standard: https://developer.mozilla.org/en-US/docs/Web/CSS/:-moz-handler-crashed"]
         const IN_HANDLER_CRASHED_STATE = 1 << 19,
+        #[doc = "https://html.spec.whatwg.org/multipage/#selector-required"]
+        const IN_REQUIRED_STATE = 1 << 20,
+        #[doc = "https://html.spec.whatwg.org/multipage/#selector-optional"]
+        const IN_OPTIONAL_STATE = 1 << 21,
         #[doc = "https://html.spec.whatwg.org/multipage/#selector-read-write"]
-        const IN_READ_WRITE_STATE = 1 << 20,
+        const IN_READ_WRITE_STATE = 1 << 22,
     }
 }

components/style/gecko/non_ts_pseudo_class_list.rs

@@ -59,6 +59,8 @@ macro_rules! apply_non_ts_list {
                     PSEUDO_CLASS_INTERNAL),
                 ("-moz-handler-crashed", MozHandlerCrashed, mozHandlerCrashed, IN_HANDLER_CRASHED_STATE,
                     PSEUDO_CLASS_INTERNAL),
+                ("required", Required, required, IN_REQUIRED_STATE, _),
+                ("optional", Optional, optional, IN_OPTIONAL_STATE, _),
                 ("read-write", ReadWrite, _, IN_READ_WRITE_STATE, _),
                 ("read-only", ReadOnly, _, IN_READ_WRITE_STATE, _),
 

components/style/gecko/wrapper.rs

@@ -707,7 +707,9 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
             NonTSPseudoClass::MozLoading |
             NonTSPseudoClass::MozHandlerBlocked |
             NonTSPseudoClass::MozHandlerDisabled |
-            NonTSPseudoClass::MozHandlerCrashed => {
+            NonTSPseudoClass::MozHandlerCrashed |
+            NonTSPseudoClass::Required |
+            NonTSPseudoClass::Optional => {
                 self.get_state().contains(pseudo_class.state_flag())
             },
             NonTSPseudoClass::ReadOnly => {