Bug 1936113 - Parse :open pseudo-class in the style system. r=dshin

This enables us to parse the pseudo, but it's not yet connected to anything.

Differential Revision: https://phabricator.services.mozilla.com/D234092

dom/base/rust/lib.rs

@@ -134,6 +134,9 @@ bitflags! {
         /// https://drafts.csswg.org/css-scoping-1/#the-has-slotted-pseudo
         /// Match whether a slot element has assigned nodes
         const HAS_SLOTTED = 1u64 << 48;
+        /// https://drafts.csswg.org/selectors-4/#open-state
+        /// Match whether an openable element is currently open
+        const OPEN = 1u64 << 49;
 
         /// Some convenience unions.
         const DIR_STATES = Self::LTR.bits() | Self::RTL.bits();

servo/components/style/gecko/non_ts_pseudo_class_list.rs

@@ -53,6 +53,7 @@ macro_rules! apply_non_ts_list {
                 ("-moz-styleeditor-transitioning", MozStyleeditorTransitioning, STYLEEDITOR_TRANSITIONING, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),
                 ("fullscreen", Fullscreen, FULLSCREEN, _),
                 ("modal", Modal, MODAL, _),
+                ("open", Open, OPEN, _),
                 ("-moz-topmost-modal", MozTopmostModal, TOPMOST_MODAL, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),
                 ("-moz-broken", MozBroken, BROKEN, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS_AND_CHROME),
                 ("-moz-has-dir-attr", MozHasDirAttr, HAS_DIR_ATTR, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),

servo/components/style/gecko/wrapper.rs

@@ -2088,6 +2088,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
             NonTSPseudoClass::MozDirAttrLikeAuto |
             NonTSPseudoClass::Modal |
             NonTSPseudoClass::MozTopmostModal |
+            NonTSPseudoClass::Open |
             NonTSPseudoClass::Active |
             NonTSPseudoClass::Hover |
             NonTSPseudoClass::HasSlotted |