GitLab

Refactor startup tracing logic out of TracingControllerImpl and use
modern TracingSession from Perfetto client API directly.

This allows for much greater simplification, including removing
substantial amount of logic from TracingControllerImpl (including
logic for finishing trace recording after a timeout) and removing
PerfettoFileTracer.

This also allows for a clean implementation of features like streaming
trace to a file and merging browsertest and startup tracing logic.

R=eseckler@chromium.org,skyostil@chromium.org
BUG=1157954,1082916

Change-Id: Id4c608b05cbd6b0696cb8e3445888b6a9d86c797
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2587040
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839190}