Mark call notifications as critical

So that we are notified about incoming calls even while busy.

https://bugzilla.gnome.org/show_bug.cgi?id=666221

Signed-off-by: Emilio Pozuelo Monfort <emilio.pozuelo@collabora.co.uk>

js/ui/components/telepathyClient.js

@@ -1135,6 +1135,8 @@ const AudioVideoNotification = new Lang.Class({
         this.parent(source, title, null, { customContent: true });
         this.setResident(true);
 
+        this.setUrgency(MessageTray.Urgency.CRITICAL);
+
         this.addButton('reject', _("Decline"));
         /* translators: this is a button label (verb), not a noun */
         this.addButton('answer', _("Answer"));