implement M69 Native RTCPeerConnection.(addTrack|removeTrack) and sdpSemantics unified-plan support

[hthetiot]

Using sdpSementics unified-plan is causing this error

On Chrome side:

[Deprecation] "Complex" Plan B SDP detected! Chrome will switch the default sdpSemantics in M72, around January 2019 from 'plan-b' to the standardized 'unified-plan' format and this peer connection is relying on the default sdpSemantics. This SDP is not compatible with Unified Plan and will be rejected by clients expecting Unified Plan. For more information about how to prepare for the switch, see https://webrtc.org/web-apis/chrome/unified-plan/.

On iOSRTC side:

# Fatal error in: ../../pc/peerconnection.cc, line 1098
# last system error: 22
# Check failed: !IsUnifiedPlan()
# AddStream is not available with Unified Plan SdpSemantics. Please use AddTrack

This PR set SdpSemantics to UnifiedPlan by default and also handle PlanB.

To test task/libwebrtc-update-m69-unified-plan branch

cordova plugin remove cordova-plugin-iosrtc --verbose
cordova plugin add https://github.com/cordova-rtc/cordova-plugin-iosrtc#task/libwebrtc-update-m69-unified-plan
cordova platform remove ios --no-save
cordova platform add ios --no-save

[hthetiot]

@cah-dunn if you may check this, I think you going to like/need it.

[hthetiot]

ba3900f fix issue with RTCPeerConnection.addTrack|removeTrack.

Swift Camera confirmed (RTCPeerConnection.removeTrack, RTCPeerConnection.addTrack, renegotiate Offer/Awnser)

[cah-kyle-dunn]

@hthetiot Apologies, just saw your comment. I'll take a look today.

[akilude]

Hi,

Tried this branch with task/preferredCodec and it works well with iOS 12. We have specified Unified plan in our peer constraints.

Thanks for your work.

[akilude]

Hi,

Is it possible to add replaceTrack as well in addition to addTrack/removeTrack?

[hthetiot]

@akilude I will look into replaceTrack keep you posted.

[hthetiot]

@akilude ReplaceTrack is too recent, I will need more work and possibly to update WebRTC for that.
In the mean time, addTrack+removeTrack+renegociate work great.

[akilude]

I understand @hthetiot , thanks for the update