cleanup: Port non-GObject classes to JS6 classes

ES6 finally adds standard class syntax to the language, so we can
replace our custom Lang.Class framework with the new syntax. Any
classes that inherit from GObject will need special treatment,
so limit the port to regular javascript classes for now.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/361

js/ui/status/system.js

@@ -4,7 +4,6 @@ const AccountsService = imports.gi.AccountsService;
 const Clutter = imports.gi.Clutter;
 const Gio = imports.gi.Gio;
 const GLib = imports.gi.GLib;
-const Lang = imports.lang;
 const Shell = imports.gi.Shell;
 const St = imports.gi.St;
 const GObject = imports.gi.GObject;
@@ -16,10 +15,8 @@ const PanelMenu = imports.ui.panelMenu;
 const PopupMenu = imports.ui.popupMenu;
 
 
-var AltSwitcher = new Lang.Class({
-    Name: 'AltSwitcher',
-
-    _init(standard, alternate) {
+var AltSwitcher = class {
+    constructor(standard, alternate) {
         this._standard = standard;
         this._standard.connect('notify::visible', this._sync.bind(this));
         if (this._standard instanceof St.Button)
@@ -42,7 +39,7 @@ var AltSwitcher = new Lang.Class({
         this.actor = new St.Bin();
         this.actor.connect('destroy', this._onDestroy.bind(this));
         this.actor.connect('notify::mapped', () => { this._flipped = false; });
-    },
+    }
 
     _sync() {
         let childToShow = null;
@@ -83,14 +80,14 @@ var AltSwitcher = new Lang.Class({
         }
 
         this.actor.show();
-    },
+    }
 
     _onDestroy() {
         if (this._capturedEventId > 0) {
             global.stage.disconnect(this._capturedEventId);
             this._capturedEventId = 0;
         }
-    },
+    }
 
     _onCapturedEvent(actor, event) {
         let type = event.type();
@@ -101,7 +98,7 @@ var AltSwitcher = new Lang.Class({
         }
 
         return Clutter.EVENT_PROPAGATE;
-    },
+    }
 
     _onLongPress(action, actor, state) {
         if (state == Clutter.LongPressState.QUERY ||
@@ -112,14 +109,11 @@ var AltSwitcher = new Lang.Class({
         this._sync();
         return true;
     }
-});
+};
 
-var Indicator = new Lang.Class({
-    Name: 'SystemIndicator',
-    Extends: PanelMenu.SystemIndicator,
-
-    _init() {
-        this.parent();
+var Indicator = class extends PanelMenu.SystemIndicator {
+    constructor() {
+        super();
 
         let userManager = AccountsService.UserManager.get_default();
         this._user = userManager.get_user(GLib.get_user_name());
@@ -146,7 +140,7 @@ var Indicator = new Lang.Class({
 
         Main.sessionMode.connect('updated', this._sessionUpdated.bind(this));
         this._sessionUpdated();
-    },
+    }
 
     _updateActionsVisibility() {
         let visible = (this._settingsAction.visible ||
@@ -155,18 +149,18 @@ var Indicator = new Lang.Class({
                        this._altSwitcher.actor.visible);
 
         this._actionsItem.actor.visible = visible;
-    },
+    }
 
     _sessionUpdated() {
         this._settingsAction.visible = Main.sessionMode.allowSettings;
-    },
+    }
 
     _updateMultiUser() {
         let hasSwitchUser = this._loginScreenItem.actor.visible;
         let hasLogout = this._logoutItem.actor.visible;
 
         this._switchUserSubMenu.actor.visible = hasSwitchUser || hasLogout;
-    },
+    }
 
     _updateSwitchUserSubMenu() {
         this._switchUserSubMenu.label.text = this._user.get_real_name();
@@ -199,7 +193,7 @@ var Indicator = new Lang.Class({
             this._switchUserSubMenu.icon.add_style_class_name('default-icon');
             this._switchUserSubMenu.icon.remove_style_class_name('user-icon');
         }
-    },
+    }
 
     _createActionButton(iconName, accessibleName) {
         let icon = new St.Button({ reactive: true,
@@ -209,7 +203,7 @@ var Indicator = new Lang.Class({
                                    style_class: 'system-menu-action' });
         icon.child = new St.Icon({ icon_name: iconName });
         return icon;
-    },
+    }
 
     _createSubMenu() {
         let bindFlags = GObject.BindingFlags.DEFAULT | GObject.BindingFlags.SYNC_CREATE;
@@ -340,11 +334,11 @@ var Indicator = new Lang.Class({
                                        () => { this._updateActionsVisibility(); });
         this._altSwitcher.actor.connect('notify::visible',
                                         () => { this._updateActionsVisibility(); });
-    },
+    }
 
     _onSettingsClicked() {
         this.menu.itemActivated();
         Main.overview.hide();
         this._settingsApp.activate();
     }
-});
+};