This is a reland of f991465b

Original change's description:
> [wasm] Publish new code from the background threads.
> 
> R=clemensh@chromium.org
> BUG=v8:7921
> 
> Change-Id: Ib86cb5f742907b6e54365827facfc765867ca22e
> Reviewed-on: https://chromium-review.googlesource.com/1156384
> Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
> Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54985}

Bug: v8:7921
Change-Id: I08c5eb689fe4f8ef2f7b576f0145eb0ae617fd9d
Reviewed-on: https://chromium-review.googlesource.com/1170603Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55042}