Tracing: Start the tracing service on-demand

Instead of each process connecting to the tracing service
on startup, the tracing service is now instead brought
up on demand (when something binds the Coordinator interface)
and will then pass pointers to the AgentRegistry and
PerfettoService to the other services so they can register themselves.

This is a prerequisite to having the tracing service run as a
sandboxed service (or we would always have a new background process

Requires these prior CLs for service_manager manifest support:
* (for trivial CrOS change)

Bug: 914579
Change-Id: Ia1c92fe2aa75e3411efbd119cb9443e8a78e4c8f
Commit-Queue: oysteine <>
Reviewed-by: Tom Sepez <>
Reviewed-by: Kentaro Hara <>
Reviewed-by: Eric Seckler <>
Reviewed-by: Sami Kyöstilä <>
Reviewed-by: Ehsan Chiniforooshan <>
Reviewed-by: Ken Rockot <>
Cr-Commit-Position: refs/heads/master@{#625059}
35 files changed