Perfetto: Enable by default everywhere

This enables Perfetto (https://www.perfetto.dev/) by default as the new
backend for the Chrome tracing system (what drives about://tracing).

R=ssid@chromium.org
TBR=nasko@chromium.org

Bug: 839084
Change-Id: I6a239424aaa69aa38143ec10f30636c12e858d29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1508695
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641407}