webrtc-pc

573e1b0e - Add ufrag to IceCandidate, and use IceCandidate for end-of-candidates.

Add ufrag to IceCandidate, and use IceCandidate for end-of-candidates. Since RTCIceCandidate can be used for end-of-candidates, all the attributes besides "ufrag" now become nullable. Rebase of PR #757. Fixes #726.