The default values ensure that the controller doesn't change scheduling if no
values are reported from the embedder.

This allows for switching the flag on the embedder side.

Bug: chromium:948807
Change-Id: Ib478adc1185ed5e56d06ba4404d6cafb196cff78
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1672930Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62330}