Because RtcEventLog is created and stopped in different threads,
SequencedTaskChecker causes failure at the end of a test.
Bug: none
Change-Id: Ibaec3162eedebd180b101ec46a171efee5fe667e
Reviewed-on: https://webrtc-review.googlesource.com/5401
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20078}