Go to the themes feature.
Tap the refresh button to start refreshing the list.
Tap a theme to view its detail while the refresh icon is spinning.
On the detail page, notice the spinner is visible and it overlaps the actionbar extras menu.
Bonus: Tap back to return to the themes list. Now you have two refresh spinners, overlapping each other, one of which is still rotating.
2.5 beta 4
Nexus 4 / 4.3