Perf tests: Add --fixed-test-time-with-warmup Warmup trials combined with fixed-test-time was broken recently. It was already fragile and only worked when parameters were provided in the right order. On Android we're relying on this combination to get steady results without hitting thermal limits. To address this: - Add a new parameter that encapsulates the combination - ASSERT that flags aren't provided in unsupported combinations Test: python3 restricted_trace_perf.py --fixedtime 10 Bug: angleproject:7755 Change-Id: I56fce1f65d4f0538e623951163a9c8736cb3fb03 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4027282 Reviewed-by: Roman Lavrov <romanl@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Cody Northrop <cnorthrop@google.com>