archlinux: annoying missing icons

I had a fresh install of Archlinux running GDM with Gnome and Xfce.
After installing a couple of apps (Firefox and Chrome) the icons were missing in the menu entries.

By running the below command as root and restart, the issue is fixed.

# gtk-update-icon-cache -t -f /usr/share/icons/hicolor


References:
- https://bbs.archlinux.org/viewtopic.php?id=129988