PSA: dependency descriptor and video-layers-allocation extensions are negotiated by default in M123 when simulcast is used

[Philipp Hancke]

As of

https://chromiumdash.appspot.com/commit/6a3bbefd583dfbc1c0cb1013dda17a26da3f989d

which just landed in the M123 branch, If you negotiate simulcast using addTransceiver followed by createOffer,

the resulting offer will contain the extmap lines for the AV1 dependency descriptor and the video layers allocation RTP header extensions.

If you don't want this you can use the header extensions API

  https://w3c.github.io/webrtc-extensions/#rtp-header-extension-control

to disable those extensions.

Philipp,

hoping the change sticks this time

[Philipp Hancke]

Also note that as of

  https://chromiumdash.appspot.com/commit/657b65fa188fbb2ddd18307e55af4847e44c0e0f

the negotiation of TWCCv2 changes and you now need to explicitly enableit if you want it.