popup-menu: Expand switch menu items

Given that our menus contain at most two columns, all switch widgets
in menus end up in the last columns, and thus aligned with the right
menu edge.
However, the updated user status menu will contain a section which
ignores the menu's column layout, so the switch might end up in
the middle of the menu if the overall width is determined by said
section.
At least for now, we always want the switch to align with the end,
so just expand switch menu items rather than adding an option.

https://bugzilla.gnome.org/show_bug.cgi?id=652837

js/ui/popupMenu.js

@@ -717,7 +717,8 @@ PopupSwitchMenuItem.prototype = {
         this.addActor(this.label);
 
         this._statusBin = new St.Bin({ x_align: St.Align.END });
-        this.addActor(this._statusBin, { align: St.Align.END });
+        this.addActor(this._statusBin,
+                      { expand: true, span: -1, align: St.Align.END });
 
         this._statusLabel = new St.Label({ text: '',
                                            style_class: 'popup-inactive-menu-item'