Goal is to make PeerConnectionInterface methods pure virtual.
This is a split of cl https://webrtc-review.googlesource.com/c/src/+/340143 in order to be able to fix Chromium test RTCPeerConnectionHandlerTest.OnRenegotiationNeeded
Bug: none
Change-Id: I5eac4d9a96c1b594c9e2b3505ef2466046065dc8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/340481
Auto-Submit: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41798}
3fe69c504c