Currently we rely on tasks to invoke the second pass phantom callbacks.

This may accumulate phantom callbacks and make GCs ineffective if we
do not enter the message loop to run the tasks between the GCs.

Bug: v8:7912
Change-Id: I799c97ff99ed6967480bda24ea0bf1c6a7dd69be
Reviewed-on: https://chromium-review.googlesource.com/1122621
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54144}