[webrtc-pc] new commits pushed by alvestrand

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

* Make "candidate" non-nullable in addIceCandidate parameter table.

Fixes #1077.

It's non-nullable everywhere else, but we forgot to update this table.
  by Taylor Brandstetter
https://github.com/w3c/webrtc-pc/commit/b88028da0301601fd39e184334321f412e517a01

* Also remove obsolete reference to candidate being null.
  by Taylor Brandstetter
https://github.com/w3c/webrtc-pc/commit/e2a30c2b0c9d771970decdb8f80d8f76efb5b36f

* Merge pull request #1088 from taylor-b/issue_1077_candidate_not_nullable

Make "candidate" non-nullable in addIceCandidate parameter table.
  by Harald Alvestrand
https://github.com/w3c/webrtc-pc/commit/654f482a325423e1b9dc12f855d4b8e92929bc3b