Minor clean up of BUILD file.
Add explicit events for begin and end of log.
Add a helper function to populate timestamps.
Add a GroupKey method that will be used for grouping events by for example SSRC in additon to event type.
Bug: webrtc:11933
Change-Id: Ie3c5f5a5582c89805a0273f4b27978f47ed0fb4f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/234260
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35725}
c15bced118