By default, enable one-shot optimization.

BUG=v8:8072

Change-Id: I353eb05325b9abfa9b9fab48cf47bad2891798e9
Reviewed-on: https://chromium-review.googlesource.com/1181901Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Chandan Reddy <chandanreddy@google.com>
Cr-Commit-Position: refs/heads/master@{#55247}