RTCRtpSender with a null transport?

[fippo]

while trying to implement addTrack in adapter I ran into the issue that I could not create RTCRtpSender with a null transport.
http://draft.ortc.org/#rtcrtpsender-operation*
Should that be allowed? setTransport could later be used to set the transport.

(for adapter i'll probably just create the ice gatherer, ice transport and dtls transport during addTrack. Seems wrong in terms of semantics but... this is 1.0 and so I am getting used to things feeling wrong)

[taylor-b]

In addition to being convenient from an API perspective, creating a sender without a transport could have practical benefits. An application may want to create and setup a sender without a transport as soon as possible, since this (I assume) would trigger encoder initialization. Thus, making call setup slightly faster once the application is actually ready for a call.