dbusService: Watch shell name from implementation

The service implementation already has to resolve the shell's
unique name to exclude it from sender tracking.

It can just as well take care of watching the shell D-Bus name,
which simplifies the code and will allow for more flexibility
when handling the shell disappearing from the bus.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3463>

js/dbusServices/dbusService.js

@@ -23,7 +23,15 @@ export class ServiceImplementation {
         this._senders = new Map();
         this._holdCount = 0;
 
-        this._shellName = this._getUniqueShellName();
+        // Bail out when not running under gnome-shell
+        Gio.DBus.watch_name(Gio.BusType.SESSION,
+            'org.gnome.Shell',
+            Gio.BusNameWatcherFlags.NONE,
+            (c, name, owner) => (this._shellName = owner),
+            () => {
+                this._shellName = null;
+                this.emit('shutdown');
+            });
 
         this._hasSignals = this._dbusImpl.get_info().signals.length > 0;
         this._shutdownTimeoutId = 0;
@@ -156,26 +164,6 @@ export class ServiceImplementation {
             that._queueShutdownCheck();
         };
     }
-
-    _getUniqueShellName() {
-        try {
-            const res = Gio.DBus.session.call_sync(
-                'org.freedesktop.DBus',
-                '/org/freedesktop/DBus',
-                'org.freedesktop.DBus',
-                'GetNameOwner',
-                new GLib.Variant('(s)', ['org.gnome.Shell']),
-                null,
-                Gio.DBusCallFlags.NONE,
-                -1,
-                null);
-            const [name] = res.deepUnpack();
-            return name;
-        } catch (e) {
-            console.warn(`Failed to resolve shell name: ${e.message}`);
-            return '';
-        }
-    }
 }
 Signals.addSignalMethods(ServiceImplementation.prototype);
 
@@ -189,13 +177,6 @@ export class DBusService {
     }
 
     async runAsync() {
-        // Bail out when not running under gnome-shell
-        Gio.DBus.watch_name(Gio.BusType.SESSION,
-            'org.gnome.Shell',
-            Gio.BusNameWatcherFlags.NONE,
-            null,
-            () => this._loop.quit());
-
         this._service.register();
 
         let flags = Gio.BusNameOwnerFlags.ALLOW_REPLACEMENT;