The deadlock should be fixed with https://crrev.com/c/1002174.

This is a reland of 4d1c2907

Original change's description:
> Reland "[d8][wasm] Test wasm compilation completion"
>
> This is a reland of ed2605f0
>
> Original change's description:
> > [d8][wasm] Test wasm compilation completion
> >
> > d8 was recently changed to keep running until wasm compilation has
> > completed. This adds a message test to test that.
> >
> > R=ahaas@chromium.org
> >
> > Change-Id: I73af53b6df4ee5f9a6afd26cf2d71a269140465f
> > Reviewed-on: https://chromium-review.googlesource.com/966184
> > Reviewed-by: Andreas Haas <ahaas@chromium.org>
> > Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#52008}
>
> Change-Id: Iadbd5056dfa58da454956c4e89369af8b0455b35
> Reviewed-on: https://chromium-review.googlesource.com/975242
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52154}

Bug: chromium:824681
Change-Id: I4077645bcfcb2320f6573bb779027add36feee3f
Reviewed-on: https://chromium-review.googlesource.com/999632
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52505}