This change gets the streaming compile APIs closer to their final shape,
by moving to a promise-based design.

Bug: chromium:747396
Bug: v8:6619
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ifd22ff83c79391a0f2a8ec2e5af39f71df1ea1c2
Reviewed-on: https://chromium-review.googlesource.com/581412
Commit-Queue: Brad Nelson <bradnelson@chromium.org>
Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46821}