Weak callbacks should not trigger recursive GCs during first round callbacks.
Any non-trivial work is supposed to be enqueued in the second round of
callbacks.

Bug: chromium:843903
Change-Id: Ieba58f31bab54c95b7d4027d3e16ee2d765438e7
Reviewed-on: https://chromium-review.googlesource.com/c/1340285
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57581}