This has been on by default and the flag itself is no
longer useful.

R=jarin@chromium.org, mslekova@chromium.org

Bug: v8:7790
Change-Id: Icdf111b974a01953ea775ccb96d50217f3c8321b
Reviewed-on: https://chromium-review.googlesource.com/c/1342918
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57637}