Not used yet apart from tests.

BUG=v8:7308

Change-Id: Ibbe12597007cba123236c9fab85c524df3d5dd4a
Reviewed-on: https://chromium-review.googlesource.com/955427
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51876}