This ensures that the actual instructions are in their final form when
adding them to the NativeModule.

R=titzer@chromium.org

Change-Id: Ia20698823e5a18a3c3ef7d2370769b70addfc4e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1532075
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60384}