[webrtc-pc] new commits pushed by aboba

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

* Rejection of RTCPeerConnection.peerIdentity

...should result in a new value being created.

Closes #1513.
  by Martin Thomson
https://github.com/w3c/webrtc-pc/commit/d9a413e3a1594ee490119c92b43b8d9ea08deea2

* Refactor
  by Martin Thomson
https://github.com/w3c/webrtc-pc/commit/14c608e8c484b642c08eb1ae46a3b2c96fd8ef46

* Merge pull request #1900 from martinthomson/issue1513

Clarify rejection rules for peerIdentity promise
  by Bernard Aboba
https://github.com/w3c/webrtc-pc/commit/bcfc5ae56ae75b0d519d086b7fc9e31ebd3ea65d