With recent changes, we resolve the promise of e.g. WebAssembly.compile
with the external API, and not the V8-internal API. The external API,
however, also handles microtasks, and depending on the MicrotasksPolicy,
may also execute microtasks immediately. This means the then-handler of
WebAssembly.compile may get executed within all the scopes that were
open when the external API was called. One of the open scopes is the
CancelableTask that finishes WebAssembly compilation.

The deadlock seen in the issue arises now when {quit()} gets called in
the then-handler of WebAssembly compilation.  The reason is that
{quit()} terminates the isolate, and during isolate termination, we wait
for all running CancelableTasks to finish. This, however, means a
deadlock, because the task that terminates the isolate is waiting for
itself to finish.

R=jkummerow@chrommium.org

Bug: chromium:1338150
Change-Id: I89243daffc76a456293519e24bfaad88277bb99a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717990Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81311}