This CL only affects non-production code. In non-production code, test
runners may invoke tasks (base::RunLoop()) with an interesting stack.
V8 assumes that it can clear certain data structures when running from
a non-nested task due to not having any interesting stack on top.
During testing this can lead to UAF on stack as data structures are
prematurely cleared.

With cppgc this failure can be fixed as the information on whether
test runners invoke tasks with a non-trivial stack is actually
present.

Example failure: https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8847453411432681120/+/steps/webkit_unit_tests__with_patch__on_Ubuntu-18.04/0/logs/Flaky_failure:_WebSocketStreamTest.ConnectWithFailedHandshake__status_CRASH_SUCCESS_/0

Change-Id: Ib9f6fb2d8a1aa43d0b973afeb2d0a740c769e784
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2891574Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74539}