import() is shipping by default in Chrome 63 and import.meta is
shipping in Chrome 64 already.

The flag still exists so that embedders can turn off the feature
if required.

Bug: v8:5785, v8:6693
Change-Id: Ie6c8f90927958022900f677ea5a771527111aece
Reviewed-on: https://chromium-review.googlesource.com/889658
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50913}