Reason for revert:
Breaks fuzzer.
Original issue's description:
> Only compare sequence numbers from the same SSRC in ForwardErrorCorrection.
>
> Prior to this CL, the ForwardErrorCorrection state would be reset whenever
> the difference in sequence numbers of the last recovered media packet
> and the new packet (media or FEC) was too large. This comparison did not
> take into account that FlexFEC uses a different SSRC for the FEC packets,
> meaning that the the state would be reset very frequently when FlexFEC
> is used. This should not have led to any major problems, except for a
> decreased decoding efficiency.
>
> This CL verifies that whenever we compare sequence numbers in
> ForwardErrorCorrection, they do indeed belong to the same SSRC.
>
> BUG=webrtc:5654
>
> Review-Url: https://codereview.webrtc.org/2893293003
> Cr-Commit-Position: refs/heads/master@{#18399}
> Committed: 1476a9d789TBR=stefan@webrtc.org,holmer@google.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5654
Review-Url: https://codereview.webrtc.org/2919313005
Cr-Commit-Position: refs/heads/master@{#18446}
Prior to this CL, the ForwardErrorCorrection state would be reset whenever
the difference in sequence numbers of the last recovered media packet
and the new packet (media or FEC) was too large. This comparison did not
take into account that FlexFEC uses a different SSRC for the FEC packets,
meaning that the the state would be reset very frequently when FlexFEC
is used. This should not have led to any major problems, except for a
decreased decoding efficiency.
This CL verifies that whenever we compare sequence numbers in
ForwardErrorCorrection, they do indeed belong to the same SSRC.
BUG=webrtc:5654
Review-Url: https://codereview.webrtc.org/2893293003
Cr-Commit-Position: refs/heads/master@{#18399}
