In this CL:
- Moved critical section out of RtpFrameReferenceFinder.
- RtpFrameReferenceFinder can now assign picture ids with an offset.
- RtpVideoStreamReceiver will now reset the |reference_finder_| in case
of a codec switch.
Bug: webrtc:10795, webrtc:10828
Change-Id: I22631c121a465c434de24af5ce8be2a647fe3556
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/154353
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29317}