Derived projects need easy access to the original V8's implementation of
time to implement Platform interface.

Bug: chromium:751993
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I97ee77929fda5930e7d75ca8609797673485cec3
Reviewed-on: https://chromium-review.googlesource.com/636884Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Sergei Datsenko <dats@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47638}