Bug 1883209 - Disable harder wayland's appmenu support. r=stransky

Until it has a final shape, at least, since there's ongoing work and
discussion in the MR.

Differential Revision: https://phabricator.services.mozilla.com/D203933

modules/libpref/init/StaticPrefList.yaml

@@ -15960,6 +15960,15 @@
   value: false
   mirror: always
 
+# Whether GTK global menubar support is enabled using wayland's experimental
+# dbus_annotation protocol:
+# https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/52
+# Disabled until it has a final shape and it is available in compositors.
+- name: widget.gtk.global-menu.wayland.enabled
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 # Whether native GTK context menus are enabled.
 # Disabled because at the very least there's missing custom icon support.
 - name: widget.gtk.native-context-menus

widget/gtk/NativeMenuGtk.cpp

@@ -735,6 +735,9 @@ void DBusMenuBar::OnNameOwnerChanged() {
 
 #  ifdef MOZ_WAYLAND
   if (auto* display = widget::WaylandDisplayGet()) {
+    if (!StaticPrefs::widget_gtk_global_menu_wayland_enabled()) {
+      return;
+    }
     xdg_dbus_annotation_manager_v1* annotationManager =
         display->GetXdgDbusAnnotationManager();
     if (NS_WARN_IF(!annotationManager)) {