screenShield: Do not save lock state on wayland

We keep track of the lock state and restore it on startup to prevent
a crash from bypassing the screen lock. However on wayland, a crash
doesn't result in gnome-session restarting gnome-shell, but brings
down the entire session - that is, restoring the lock state does not
actually protect the existing session in that case, but forces the
user to authenticate twice in order to start the next session. This
is clearly not helpful, so avoid this by not saving the state when
running as wayland compositor.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/17

js/ui/screenShield.js

@@ -1283,6 +1283,9 @@ var ScreenShield = new Lang.Class({
 
         this._resetLockScreen({ animateLockScreen: animate,
                                 fadeToBlack: true });
+        // On wayland, a crash brings down the entire session, so we don't
+        // need to defend against being restarted unlocked
+        if (!Meta.is_wayland_compositor())
             global.set_runtime_state(LOCKED_STATE_STR, GLib.Variant.new('b', true));
 
         // We used to set isActive and emit active-changed here,