dateMenu: Relayout IndicatorPad when parent size changes

This happens often in resource-scaled world

https://bugzilla.gnome.org/show_bug.cgi?id=765011

js/ui/dateMenu.js

@@ -379,6 +379,7 @@ class IndicatorPad extends St.Widget {
     _init(actor) {
         this._source = actor;
         this._source.connect('notify::visible', () => { this.queue_relayout(); });
+        this._source.connect('notify::size', () => { this.queue_relayout(); });
         super._init();
     }