Until now lookbehind assertions have been quantifiable in non-unicode regexps.
This seems to be an oversight in the spec.

R=jgruber@chromium.org

Bug: v8:7462
Change-Id: Iad0db441089c7510dd2c42a861db92c05545ce1e
Reviewed-on: https://chromium-review.googlesource.com/926102
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51392}

It was shipped in Chrome 62.

Bug: v8:5546, v8:4829
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I3ac318639f1f7483d4d4f4fe5606387a856be98a
Reviewed-on: https://chromium-review.googlesource.com/777940Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49687}

Both of these features were shipped in Chrome 62.

Bug: v8:4545, v8:6172
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Ie00dcbeded7517a15696d4a78fcfbbf162919923
Reviewed-on: https://chromium-review.googlesource.com/775601Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49453}

This flag has been on by default since Chrome 61.

Bug: v8:5549
Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I81c34d1d3a7dbd219acce2cdf0cf4917eb484002
Reviewed-on: https://chromium-review.googlesource.com/738312Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48945}