remote-outbound-rtp/remote-inbound-rtp not available on peer (browser)

[maxammann]

Engineer from KittyCAD/Zoo here.

I'm trying to get RTT statistics on the browser side (Chrome) but having trouble. Essentially, the remote-outbound-rtp statistics are not available. On the Rust side the remote-inbound-rtp stats are available (as implemented in #282).

I suspenct that the webrtc create somehow does not send support the necessary features such that the browser can emit the statistics.

However, I could validate that the webrtc crate sends RTCP Sender Reports. DLRR extensions also seem necessary for RTT calculation, but not so sure.

We also use register_default_interceptors so RTCP messages should be handled correctly.