Launching too many parallel tasks near OOM increases risk of allocation
failure during GC and OOM crash.

Bug: chromium:824214, v8:7605
Change-Id: I336d1f01e4005fb2a8e16ef92f40532b8ed83f2c
TBR: mlippautz@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/983919
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52282}