[webrtc-pc] new commits pushed by alvestrand

The following commits were just pushed by alvestrand to https://github.com/w3c/webrtc-pc:

* Selected candidate pair behavior

Fix for Issue https://github.com/w3c/webrtc-pc/issues/1981

Rebase of https://github.com/w3c/webrtc-pc/pull/2269
  by Bernard Aboba
https://github.com/w3c/webrtc-pc/commit/41e5025588e39cd53e9c7e0ded39ede2ce189dda

* Merge pull request #2290 from w3c/aboba-patch-12

Selected candidate pair behavior
  by Harald Alvestrand
https://github.com/w3c/webrtc-pc/commit/81886a36bb448d960995c357090746284c893c4b