The main pieces of this refactor are splitting up the creation of
simulcast layers for screenshare or the normal case, more consistent
naming, renaming streams to layers and trying to be more explicit with
some of the logic. Also added TODOs for future work to put more
application control into creating simulcast streams.
Bug: webrtc:8785
Change-Id: Ibf49fa0cc6d890ff96f8ee11c89d93a2c94119d6
Reviewed-on: https://webrtc-review.googlesource.com/47580
Commit-Queue: Seth Hampson <shampson@webrtc.org>
Reviewed-by: Peter Thatcher <pthatcher@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21989}
1370e309e7