[webrtc-pc] Some JSEP "applying a description" steps can't occur in parallel.

taylor-b has just created a new issue for https://github.com/w3c/webrtc-pc:

== Some JSEP "applying a description" steps can't occur in parallel. ==
The "apply a description according to JSEP" step is described as occurring entirely in parallel. But some of the JSEP steps involve creating transceivers (from new "m=" sections in a remote description) or changing their `mid` attribute, which can't occur in parallel.

So, would it be acceptable to say "In parallel, apply the description according to JSEP, performing all steps except those that modify the set of transceivers," calling out the transceiver-related steps in the "queued task" section (which we already do for the most part)?

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1177 using your GitHub account