[webrtc-pc] new commits pushed by aboba

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

* Corrected strange use of exception in event firing.
  by stefhak
https://github.com/w3c/webrtc-pc/commit/a45ef374a1530cd44fd8eff2d51fc484306aa61b

* Merge pull request #1971 from stefhak/nooperationerrorevent

Added error detail "datachannel-id-generation-error", using in error …
  by Bernard Aboba
https://github.com/w3c/webrtc-pc/commit/ae0d095271546966f2b913e03297d2be05009bb9