nharper@ is actively working on deprecating this. I believe the timeframe is 68 desktop and 69 Android, which may be easier than trying to get something working for a single release, for Android (i.e. assuming we're not going to solve it within the next week) and then trying to gracefully rip it all out.

Channel ID is being deprecated in M68 (except Android, which is M69), but ChannelIDService is also used for Token Binding, and there aren't any plans to deprecate/remove Token Binding yet.

@nharper: Is the plan to still expose it to extensions? If it's kept wholly in the network service, it seems significantly easier to figure out what needs to be done - but given the current API is related to CID, I wasn't sure.

There isn't any plan to not expose Token Binding IDs (formerly Channel IDs) to extensions. (The includeTlsChannelId extension API exposes both Channel IDs and Token Binding IDs - it isn't limited to just Channel ID right now.)

If we want to deprecate includeTlsChannelId, the first step would probably be to add UMA metrics to it to get a sense of how much it's being used. I'm guessing there are internal extensions using it that wouldn't want to see it disappear.

dougt@, assigning to you to figure out the next steps.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/302deadb0f151b3a52536a81882ada00549b11d3

commit 302deadb0f151b3a52536a81882ada00549b11d3
Author: Devlin Cronin <rdevlin.cronin@chromium.org>
Date: Wed Jul 18 14:25:28 2018

[Extensions] Add metrics for including TLS channel ID

Bug:  840412 
Change-Id: I3da214023c2e896266e171cb153d367c43d6b2ba
Reviewed-on: https://chromium-review.googlesource.com/1141069
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Nick Harper <nharper@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576043}
[modify] https://crrev.com/302deadb0f151b3a52536a81882ada00549b11d3/extensions/browser/api/messaging/message_service.cc
[modify] https://crrev.com/302deadb0f151b3a52536a81882ada00549b11d3/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/302deadb0f151b3a52536a81882ada00549b11d3/tools/metrics/histograms/histograms.xml

currently, we are looking at the usage of Token Binding and Channel ID. We probably won't be migrating this to network service. We need to check the behavior of not migrating this next.

removing Proj-Servicification-Canary. Not blocking canary.

See bug 875053.