The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b4c3e80831e073dfb051d97f129c9de070cbc4eb

commit b4c3e80831e073dfb051d97f129c9de070cbc4eb
Author: Yuwei Huang <yuweih@chromium.org>
Date: Wed Jan 10 19:36:40 2018

[CRD iOS] Improve third party auth failure message

Third party auth is currently not supported on iOS. For now when the user
connects to a corp device, they will only see a snackbar saying
"[ThirdPartyAuth] unable to authenticate with <machine name>", which is
confusing to the user.

This CL improves it by making the text clearer, and refactors the logic
a bit so that the message is displayed by ClientConnectionVC instead of
RemotingClient.

Bug:  793167 
Change-Id: I5bceb6163149913e1293896415d36ca8e5e69038
Reviewed-on: https://chromium-review.googlesource.com/849490
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528383}
[modify] https://crrev.com/b4c3e80831e073dfb051d97f129c9de070cbc4eb/remoting/ios/app/client_connection_view_controller.mm
[modify] https://crrev.com/b4c3e80831e073dfb051d97f129c9de070cbc4eb/remoting/ios/domain/client_session_details.h
[modify] https://crrev.com/b4c3e80831e073dfb051d97f129c9de070cbc4eb/remoting/ios/session/remoting_client.mm
[modify] https://crrev.com/b4c3e80831e073dfb051d97f129c9de070cbc4eb/remoting/resources/remoting_strings.grd

Is there a reference inside the documentation that defines "ThirdPartyAuth".

I was thinking that the documentation page for the iOS Chromoting app should  state at the very bottom which authentication methods are support and explicitly state that the method used by google.com is not supported.

For documentation page, are you talking about go/chromoting-ios? I can add the list of known issue to that page.

Verifed Fixed in 67.3396.22