Add helper class to process RtcEventLog events in order.
Use helper class to migrate rtc_event_log2rtp_dump.cc
to new parser API.
Bug: webrtc:8111
Change-Id: I7cbc220dad1f50be3a985ed44de27b38e5f20476
Reviewed-on: https://webrtc-review.googlesource.com/98601
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Elad Alon <eladalon@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24806}
