The code incorrectly assumed that codecs exist on a per-mid/transceiver
basis, but codec payload types are unique on a per-transport basis and
in practise most applications use BUNDLE (single transport for the
entire PC).
This CL makes the codecs per-transport instead of per-transceiver. We
still need to iterate transceivers because codecs are exposed on a
per-transceiver basis and as shown in
https://jsfiddle.net/henbos/7kqxgnr8/ it is possible for FMTP lines to
be different on different m= sections despite BUNDLE.
Manual testing shows that this CL brings down the number of "codec"
stats in Google Meet 50p from 872 objects to 43 objects.
Bug: webrtc:14414
Change-Id: Ic854b31bd595799554b99fff22cbd48264ebd141
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/273707
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Philipp Hancke <phancke@microsoft.com>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37989}
b2be392c70