Cleanups around tracing bottlenecks and tests.

Bug: chromium:1056170
Change-Id: I1f9ddd6d8727971db3bed5294f4ff3fdd20a9e34
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2757696
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73394}