The creation and destruction of the MessageLoop and nsThread for the Android UI thread are handled in nsAppShell. Unfortunately, currently in Fennec, the nsAppShell singleton appears to never get destroyed. This makes it impossible to test the Android UI thread clean up code which contains synchronous inter-thread code. If the nsAppShell is ever destroyed in future versions of Fennec or GeckoView, the Android UI thread clean up call should be enabled and tested.

I think nsAppShell gets destroyed (or should get destroyed) when we quit/restart Fennec through Gecko (e.g. using the QuitNow addon's "Quit" menu).

(In reply to Jim Chen [:jchen] [:darchons] from comment #1) > I think nsAppShell gets destroyed (or should get destroyed) when we > quit/restart Fennec through Gecko (e.g. using the QuitNow addon's "Quit" > menu). I actually tried using an add on called Quit Firefox (for mobile) and when I selected "Quit" from the menu, Fennec would quit but we would never return from MessageLoop::Run. It appeared we were just exiting. I'll try QuitNow and see if I get different results.

QuitNow seems to actually exit from MessageLoop::Run however the nsAppShell still does not appear to be destroyed.

After more investigation, it looks like something is reffing the nsAppShell and then not unreffing it so it does not get deleted. So shutdown appears to be working as expected, is just the nsAppShell that is not getting deleted.