Rename a few Panel fields and add a _statusArea object pointing to the
status area PanelButton objects. You can now address each item
consistently from lg:
Main.panel._activities
Main.panel._appMenu
Main.panel._dateMenu
Main.panel._statusArea.a11y
Main.panel._statusArea.volume ...
Main.panel._userMenu
https://bugzilla.gnome.org/show_bug.cgi?id=646915