This implements the changes proposed at
https://github.com/tc39/ecma262/pull/916.
The API will be extended in a follow-up CL.

R=adamk@chromium.org

Bug: v8:1569
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I79476b5b674c924fea390dff1b9bee7f86a111c6
Reviewed-on: https://chromium-review.googlesource.com/544970Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46289}