The cycle mentioned in the comment has disappeared but we still need
to set the native context Ref twice, once when the broker mode is
kDisabled, and once when it's kSerializing (the earlier Ref is
invalid by that time).

Bug: v8:7790
Change-Id: I5778814a20c2706ca088557176aaa9ccfc3a39df
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2902741
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74634}