Oshima, what did we decide on this?

It never got implemented in the extension API, which is what the new Settings code relies on (DisplayInfoProvider::EnableUnifiedDesktop).

Is this something we still plan to support?

It will still be accessible on the old Settings for anyone who enables the switch, at least for now, so lowering to P2.

It's implemented on ChromeOS. I think we need an additional api to check if we the feature itself is enabled by policy/flag though.

https://cs.chromium.org/chromium/src/chrome/browser/extensions/display_info_provider_chromeos.cc?rcl=375c78221f4df786923744d9cc76e66b55775ecb&l=601

Sigh. I just discovered  issue 564650 , which makes representing unified desktop in the UI more complicated, and my change here would potentially break existing usage of the API:

https://codereview.chromium.org/2802603005

(FWIW, the existing API does not provide much information about unified desktop mode, and the comment for enableUnifiedDesktop is confusing).

My proposal is to:
1) Pass an optional parameter to getInfo to provide a 'singleUnified' result when in unified mode so that Settings can match Chrome behavior.
2) Pass an optional parameter to enableUnifiedDesktop to also change the mode. This is a little awkward, and I don't understand what the current behavior actually does, but it will at least be backwards compatible.

After further discussion with rdevlin.cronin@, I am going to leave the behavior of enableUnifiedDesktop as it was, and add isUnified to DisplayProperties so that we can set the display mode to unified similarly to how we set mirror mode.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/717b7c3c86906d088c16fb30f4588fb0a0ea15e3

commit 717b7c3c86906d088c16fb30f4588fb0a0ea15e3
Author: stevenjb <stevenjb@chromium.org>
Date: Wed Apr 12 00:59:27 2017

MD Settings: Display: Add unified desktop control and modify api

This CL:
* Updates the chrome.system.display API to support unified
  desktop for Settings UI.
* Adds a unified desktop setting to the MD Settings UI when
  the flag is enabled.

BUG= 703423 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2802603005
Cr-Commit-Position: refs/heads/master@{#463865}

[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/app/settings_strings.grdp
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/extensions/display_info_provider_chromeos.cc
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/extensions/display_info_provider_chromeos.h
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/extensions/display_info_provider_chromeos_unittest.cc
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/resources/settings/device_page/display.html
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/resources/settings/device_page/display.js
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/test/data/webui/settings/device_page_tests.js
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/chrome/test/data/webui/settings/fake_system_display.js
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/extensions/browser/api/system_display/display_info_provider.cc
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/extensions/browser/api/system_display/display_info_provider.h
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/extensions/browser/api/system_display/system_display_api.cc
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/extensions/common/api/system_display.idl
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/third_party/closure_compiler/externs/system_display.js
[modify] https://crrev.com/717b7c3c86906d088c16fb30f4588fb0a0ea15e3/third_party/closure_compiler/interfaces/system_display_interface.js

Verified on build 9460.4.0