The first CL https://chromium-review.googlesource.com/c/v8/v8/+/3010281
had a small mistake: the GC predicate alone doesn't yet guarantee that
Ref creation will succeed (due to JSFunction still being fg-serialized).

Bug: chromium:1227279, v8:11957, v8:7790
Change-Id: I81772baa66e0f778b92a03ea7941a199d92d4857
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3013353
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75627}