style: Make the document blocked by the topmost element in the top layer.

Spec: https://html.spec.whatwg.org/multipage/#blocked-by-a-modal-dialog

Depends on D86392

Differential Revision: https://phabricator.services.mozilla.com/D86227

components/style/gecko/non_ts_pseudo_class_list.rs

@@ -53,6 +53,7 @@ macro_rules! apply_non_ts_list {
                 ("-moz-styleeditor-transitioning", MozStyleeditorTransitioning, IN_STYLEEDITOR_TRANSITIONING_STATE, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),
                 ("fullscreen", Fullscreen, IN_FULLSCREEN_STATE, _),
                 ("-moz-modal-dialog", MozModalDialog, IN_MODAL_DIALOG_STATE, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),
+                ("-moz-topmost-modal-dialog", MozTopmostModalDialog, IN_TOPMOST_MODAL_DIALOG_STATE, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS),
                 // TODO(emilio): This is inconsistently named (the capital R).
                 ("-moz-focusring", MozFocusRing, IN_FOCUSRING_STATE, _),
                 ("-moz-broken", MozBroken, IN_BROKEN_STATE, _),

components/style/gecko/wrapper.rs

@@ -2063,6 +2063,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
             NonTSPseudoClass::MozDirAttrLikeAuto |
             NonTSPseudoClass::MozAutofill |
             NonTSPseudoClass::MozModalDialog |
+            NonTSPseudoClass::MozTopmostModalDialog |
             NonTSPseudoClass::Active |
             NonTSPseudoClass::Hover |
             NonTSPseudoClass::MozAutofillPreview => {