Add gnome-shell options:
--perf-iters=ITERS"
Numbers of iterations of performance module to run
--perf-warmup
Run a dry run before performance tests
Make a successful run of a performance test return 0 not non-zero,
and handle the difference between that and a 0-exit in normal
usage (meaning replaced) in the wrapper.
https://bugzilla.gnome.org/show_bug.cgi?id=618189