These tests assume that a newly-created Isolate is pristine, but that's
not true for nosnap builds.

TBR=ulan@chromium.org

Change-Id: Ie5d0fb0450f285c8eeb8e088feef6729102c0f14
Reviewed-on: https://chromium-review.googlesource.com/489063Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44952}