[webrtc-pc] new commits pushed by aboba

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

* Fix remaining compat issue with respec 19

Had to use data-dfn-for='' for RTCIdentityProvider as there is a WebIDL attribute using that same name, which prevented respec from singling out the dictionary
  by Dominique Hazael-Massieux
https://github.com/w3c/webrtc-pc/commit/9403a1b3dc67db3243ba15f55e98fd6cac928175

* Merge pull request #1767 from w3c/more-respec19-fix

Fix remaining compat issue with respec 19
  by Bernard Aboba
https://github.com/w3c/webrtc-pc/commit/347380a45ab9dd91d62774c2e43cc1fed243fa4e