Make perf tests faster in correctness-only mode. When running with "--one-frame-only" we can also skip the test warmup. Also we can reduce the internal iteration count to 1 to make the tests as fast as possible. Bug: angleproject:2923 Change-Id: I2f82ae0dd237767ea7b15074e459ed1094ba9943 Reviewed-on: https://chromium-review.googlesource.com/c/1308737 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>