My questions are:

* Is this a release blocker of the iOS client?
* Do we need to negotiate the protocol and what's the priority? Shall we always choose WebRTC if possible and chromotocol otherwise? Or shall we just simply stop supporting chromotocol in mobile clients?

It's not a blocker for the iOS release, but chromotocol is showing signs of disrepair so replacing it should be a priority after that. I would say we should continue to support chromotocol, but prefer WebRTC if available. Then, at some point we can drop support for it from both clients and hosts.

Feel free to adjust the milestone if you don't think you'll get to it in M62.

The flag to enable this is here: https://chromium-review.googlesource.com/c/chromium/src/+/599116

TURN needs authentication.

Centralized token getter is working now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5f277895cdfd29a4423f42d04c9fc0743746f5f3

commit 5f277895cdfd29a4423f42d04c9fc0743746f5f3
Author: Yuwei Huang <yuweih@chromium.org>
Date: Sat Nov 11 00:36:26 2017

[CRD iOS] UI to toggle WebRTC protocol

This CL adds a button on the SSO side menu to toggle using WebRTC
protocol in the debug build iOS client. It will make it easier to
debug the WebRTC client or do side-by-side comparison.

This CL also introduces a basic flag setting framework in iOS.

Bug: 748710
Change-Id: I6f7799964b49427330953553f048d67a7d31dce1
Reviewed-on: https://chromium-review.googlesource.com/764987
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515761}
[modify] https://crrev.com/5f277895cdfd29a4423f42d04c9fc0743746f5f3/remoting/ios/app/side_menu_items.mm
[modify] https://crrev.com/5f277895cdfd29a4423f42d04c9fc0743746f5f3/remoting/ios/persistence/remoting_preferences.h
[modify] https://crrev.com/5f277895cdfd29a4423f42d04c9fc0743746f5f3/remoting/ios/persistence/remoting_preferences.mm
[modify] https://crrev.com/5f277895cdfd29a4423f42d04c9fc0743746f5f3/remoting/ios/session/remoting_client.mm

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/55566630aa8cb582dd1da4c557950ac944fd9830

commit 55566630aa8cb582dd1da4c557950ac944fd9830
Author: Yuwei Huang <yuweih@chromium.org>
Date: Sat Nov 11 00:59:38 2017

[CRD iOS] Fix empty closure crash in AudioStreamConsumer::ProcessAudioPacket

WebRTCAudioSinkAdapter passes an empty done closure to AudioStreamConsumer.
Different from a DoNothing closure, calling an empty closure will end up
crashing the app. This CL fixes AudioStreamConsumer so that it only runs
the done closure if it is not null.

Bug: 748710
Change-Id: Ied6301b54e694f8d62618e7ed4e16fa2811a4202
Reviewed-on: https://chromium-review.googlesource.com/765010
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515771}
[modify] https://crrev.com/55566630aa8cb582dd1da4c557950ac944fd9830/remoting/client/audio/audio_stream_consumer.cc