Safari 11 bugfix: usage of promise-based version for pc.createOffer

[lawlietmester]

Initial bug: https://github.com/andyet/SimpleWebRTC/issues/704

In case of callback-based version of .createOffer Safari 11.0.3 perceives mediaConstraints always as

{
  'offerToReceiveAudio': false,
  'offerToReceiveVideo': false
}

But in case of promise-based version it perceives mediaConstraints as intended.

[fippo]

that actually sounds like a bug in adapter.

I made #98 using https://github.com/fippo/webrtc-codemods to use promises instead of the legacy version in all relevant calls

[lawlietmester]

@fippo Maybe, but https://github.com/webrtc/adapter/issues/685

Safari support will most likely be added once it's more stable and supporting API's are in place.

So in fact they are not supporting it

[fippo]

no, adapter shims the legacy offerToReceive constraints. I am just surprised this would not work in the callback version -- even though that should simply not be used anymore