Bugzilla

Some of the search browser Mochitests and many of the search XPCShell tests put test setup code inside an `add_task` call, rather than an `add_setup` call. There are at least 2 reasons this isn't a good idea:
1) `add_setup` is more explicit and semantically correct
2) When adding an `.only()` call to a task to  run that task in isolation, the setup code will not be run at all if it's inside an `add_task` call, whereas it would be run if it were inside an `add_setup` call.