Reset the instance before the test run, to ensure it runs with the
same initial state as the reference run.

R=clemensb@chromium.org

Bug: chromium:1227591
Change-Id: Ie78b4b84e3df37ab8955c240f1d41e2f5e89a5de
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3015572Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75658}