Background tracing should consume startup tracing

The startup tracing enabled by background tracing flags was
taken over by tracing controller. It should be taken over by
background tracing manager.

Change-Id: Id6a070106b46215e50c8076b4c1d67e3aa74d8c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1667744
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Commit-Queue: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671221}
5 files changed