Filing this issue based on discussion in crbug.com/650509. 

Currently QUIC is listening to SSLConfigChange and closes session when it is notified on SSL config change. An SSLConfigChange could be triggered by a bunch of signals besides channel ID. And what QUIC really cares is the channel ID: we want to close the sessions using an old channel ID when a channel ID gets deleted.

As channel ID will be deprecated soon in Q1 and expected to be removed in Q2, we will keep the API as is and mark session as going away for now. Once channel ID is removed, we should remove QUIC from being a SSLConfigService::Observer.