To avoid breaking Chromium we expose a stub method first, and will start
using it only when V8 rolls into Chromium and we implement it there.

Bug: chromium:751993
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ida1f96f2dfa833552e7adfa36a580a6ef1bdd1aa
Reviewed-on: https://chromium-review.googlesource.com/604812Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Sergei Datsenko <dats@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47233}