Various fixes necessary to get the script working with V8 6.6

Upstreamed from https://github.com/nodejs/node/pull/19201

Change-Id: Ic7819eb17cf4be8380b8c1811e569236244e7400
Reviewed-on: https://chromium-review.googlesource.com/996858
Commit-Queue: Myles Borins <mborins@google.com>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52421}