[polari] cleanup: Use proper abstract classes instead of rolling our own

[Florian Müllner <fmuellner src gnome org>]

commit 896442e8288c3aa92041c4225cb18f5a9c325835
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Aug 7 01:41:22 2019 +0200

    cleanup: Use proper abstract classes instead of rolling our own
    
    gjs now supports passing in appropriate GObject.TypeFlags, so use
    those over checking the constructor name.
    
    https://gitlab.gnome.org/GNOME/polari/merge_requests/133

 src/appNotifications.js | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
---
diff --git a/src/appNotifications.js b/src/appNotifications.js
index 8dfeb21..aa561fa 100644
--- a/src/appNotifications.js
+++ b/src/appNotifications.js
@@ -6,12 +6,10 @@ const { GLib, GObject, Gtk, Pango } = imports.gi;
 const TIMEOUT = 7;
 const COMMAND_OUTPUT_REVEAL_TIME = 3;
 
-const AppNotification = GObject.registerClass(
-class AppNotification extends Gtk.Revealer {
+const AppNotification = GObject.registerClass({
+    GTypeFlags: GObject.TypeFlags.ABSTRACT,
+}, class AppNotification extends Gtk.Revealer {
     _init() {
-        if (this.constructor.name == 'AppNotification')
-            throw new Error('Cannot instantiate abstract class AppNotification');
-
         super._init({
             reveal_child: true,
             transition_type: Gtk.RevealerTransitionType.SLIDE_DOWN
@@ -97,12 +95,10 @@ var UndoNotification = GObject.registerClass({
     }
 });
 
-const CommandOutputNotification = GObject.registerClass(
-class CommandOutputNotification extends AppNotification {
+const CommandOutputNotification = GObject.registerClass({
+    GTypeFlags: GObject.TypeFlags.ABSTRACT,
+}, class CommandOutputNotification extends AppNotification {
     _init() {
-        if (this.constructor.name == 'CommandOutputNotification')
-            throw new Error('Cannot instantiate abstract class CommandOutputNotification');
-
         super._init();
 
         this.transition_type = Gtk.RevealerTransitionType.SLIDE_UP;