This is meant to be used from the native wasm datastructures

Bug: v8:6876
Change-Id: Ie865cf3277b24f25e1845bf32837be1a24047472
Reviewed-on: https://chromium-review.googlesource.com/764502
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49310}