Ensure menu option visibility correctness

Whenever folder is changed in any way, we re-check the visibility status
for various optional menu items to make sure that they are up to date.

Through my testing, when I rapidly switch between Trash and Spam, I see
that "Empty Trash" option dynamically going away when Spam folder is
fully loaded. So this should solve the issue users are seeing.

b/11227901

Change-Id: I7a949985ec361ef76d1cd9b80cee06420a710a3b
1 file changed