Makes it safer to access from C++

Bug: v8:5751
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ib435382bd5568a62976a32b1ff4ca67c8413ddf2
Reviewed-on: https://chromium-review.googlesource.com/1127081Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54278}