Somehow I forgot to say "super.tap()" when calling "tap()" on the new
superclass, so it was just recursing infinitely but ended up actually
crashing on the first reuse of the finder.
The error was previously swallowed, I made this print it instead.
* add Android instrumentation test
* add devicelab test
* add to manifest.yaml
* rename _smoke_test.dart to _smoketest.dart to prevent flutter test from picking it up
* volatile fields; style fixes
* use ConditionVariable; fix sh script