I wouldn't anticipate any real changes are necessary*. There are few notifications on Win/Linux/Mac that aren't also on Chrome OS and it's enabled by default on CrOS (this has changed since the bug was filed a quarter ago).

Sebastien, Gary, who on the design or PM side can give us UX approval for launching on other desktops? I would like to move quickly on this because there is a cost to maintaining both code paths in terms of both engineering time and likelihood of bugs.

*There may be some need or desire to use the NativeTheme for more things (colors, fonts), but I don't think that's a launch blocker because the pre-MD notification views also use hard-coded values afaik.

That would be Hwi and Owen, who are already on this issue and aware of it.

The main reason that we haven't looked in to this yet is (was?) the launch priority of the MD notifications on Chrome OS.

Enabling them on the other platforms will primarily focus on Windows, and we'll want to make sure it feels right: do we match platform conventions (your beloved context menu), does collapsing/expanding notifications make sense, also given that there is no notification center they dismiss to, etc.

If Yoshiki and Sebastian are satisfied with the Chrome OS work and are happy to consider desktop with future changes too, then moving forward on this will largely depend on UX and Eng time on making them shine elsewhere too :).

All of these are good questions.

I would not bend over backwards to match platform conventions. Native notifications match the platform; in cases where those aren't possible to use the cost of maintaining the extra code is not a good value.

We're talking many hundreds of millions of users here. There's great value...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0839cb4844bd8e5a2e003a5545a1a60c104e5e06

commit 0839cb4844bd8e5a2e003a5545a1a60c104e5e06
Author: Finnur Thorarinsson <finnur@chromium.org>
Date: Wed Feb 07 11:46:33 2018

Notifications: Enable inline settings for new-style notifications
(when cmd line flag is specified).

Bug: 768300
Change-Id: I729658c51a4b323181c0c16416885b0efbe8bf96
Reviewed-on: https://chromium-review.googlesource.com/893383
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534981}
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/chrome/browser/notifications/platform_notification_service_impl.cc
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/ui/message_center/public/cpp/notification.h
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/ui/message_center/views/message_popup_collection.cc
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/ui/message_center/views/notification_view_md.cc
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/ui/message_center/views/notification_view_md_unittest.cc
[modify] https://crrev.com/0839cb4844bd8e5a2e003a5545a1a60c104e5e06/ui/message_center/views/notification_view_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5a64040dc63c39874d952905d188ba398464d62d

commit 5a64040dc63c39874d952905d188ba398464d62d
Author: Elly Fong-Jones <ellyjones@chromium.org>
Date: Wed Feb 07 12:37:24 2018

Revert "Notifications: Enable inline settings for new-style notifications"

This reverts commit 0839cb4844bd8e5a2e003a5545a1a60c104e5e06.

Reason for revert:

Broke Mac bots on the waterfall:
https://ci.chromium.org/buildbot/chromium/Mac/37907

../../ui/message_center/cocoa/notification_controller_unittest.mm:151:57: error: no member named 'TRAY' in 'message_center::SettingsButtonHandler'


Original change's description:
> Notifications: Enable inline settings for new-style notifications
> (when cmd line flag is specified).
> 
> Bug: 768300
> Change-Id: I729658c51a4b323181c0c16416885b0efbe8bf96
> Reviewed-on: https://chromium-review.googlesource.com/893383
> Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
> Reviewed-by: Peter Beverloo <peter@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#534981}

TBR=peter@chromium.org,finnur@chromium.org

Change-Id: I4ce487270a11ccf08f3f8ab70c5f6820f684ac24
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 768300
Reviewed-on: https://chromium-review.googlesource.com/906383
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534985}
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/chrome/browser/notifications/platform_notification_service_impl.cc
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/ui/message_center/public/cpp/notification.h
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/ui/message_center/views/message_popup_collection.cc
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/ui/message_center/views/notification_view_md.cc
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/ui/message_center/views/notification_view_md_unittest.cc
[modify] https://crrev.com/5a64040dc63c39874d952905d188ba398464d62d/ui/message_center/views/notification_view_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd

commit 4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd
Author: Finnur Thorarinsson <finnur@chromium.org>
Date: Wed Feb 07 15:52:27 2018

Notifications: Enable inline settings for new-style notifications
(when cmd line flag is specified).

TBR=peter@chromium.org

Bug: 768300
Change-Id: I8b43b902df529550a2ab66fdbdc78600baef7252
Reviewed-on: https://chromium-review.googlesource.com/906492
Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535011}
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/chrome/browser/notifications/platform_notification_service_impl.cc
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/cocoa/notification_controller_unittest.mm
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/public/cpp/notification.h
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/views/message_popup_collection.cc
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/views/notification_view_md.cc
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/views/notification_view_md_unittest.cc
[modify] https://crrev.com/4e8a8ef57d44d0972603cd3aa9ecdb0ee1524cdd/ui/message_center/views/notification_view_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b095c52864a74129bcdf38cf9b10f54104f66478

commit b095c52864a74129bcdf38cf9b10f54104f66478
Author: Finnur Thorarinsson <finnur@chromium.org>
Date: Wed Feb 14 12:41:48 2018

MD Notifications: Fix DCHECKs on Windows when showing notification.

Font metrics are calculated in two different ways on Windows,
(Chrome uses DirectWrite, unit_tests GDI), so there is a slight
offset that needs to be accounted for.

Bug: 768300
Change-Id: Ia43e95df199b9e81ca37fae64bca76a4b9cc1d3c
Reviewed-on: https://chromium-review.googlesource.com/915943
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536700}
[modify] https://crrev.com/b095c52864a74129bcdf38cf9b10f54104f66478/ui/message_center/views/notification_header_view.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/86b34748a6b96318fb88071e4d9ee33c59b03402

commit 86b34748a6b96318fb88071e4d9ee33c59b03402
Author: Finnur Thorarinsson <finnur@chromium.org>
Date: Wed Feb 14 14:03:13 2018

MD notifications: A little polish.

- Ensure Settings and Close are visible always (for non-Chrome OS).
- Add "from this site" to the "block all notifications" string.

Bug: 810873,768300
Change-Id: I85eb7753614e8cd678343d06de6160b9dac5d50d
Reviewed-on: https://chromium-review.googlesource.com/913271
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536704}
[modify] https://crrev.com/86b34748a6b96318fb88071e4d9ee33c59b03402/ui/message_center/views/notification_view_md.cc
[modify] https://crrev.com/86b34748a6b96318fb88071e4d9ee33c59b03402/ui/strings/ui_strings.grd

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2

commit bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2
Author: Finnur Thorarinsson <finnur@chromium.org>
Date: Wed Feb 14 22:46:26 2018

Notifications: Use base::Feature to switch MD notifications on/off.

- Removes command line flag.
- Adds a base::Feature switch to control it.

(for trivial header file changes)

Bug: 768300
TBR: skuhne@chromium.org, lhchavez@chromium.org, skau@chromium.org, dtrainor@chromium.org, derat@chromium.org
Change-Id: I79e97b4eed9e8493e0b49571d7785f98b99a1c2c
Reviewed-on: https://chromium-review.googlesource.com/906529
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536855}
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ash/message_center/message_list_view.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ash/system/screen_security/screen_capture_tray_item.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ash/system/screen_security/screen_share_tray_item.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ash/system/tray_accessibility.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ash/system/tray_caps_lock.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/about_flags.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/chromeos/arc/arc_migration_guide_notification.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/chromeos/printing/cups_print_job_notification.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/download/notification/download_item_notification.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/notifications/message_center_notifications_browsertest.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/notifications/platform_notification_service_impl.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/chrome/browser/ui/ash/network/network_state_notifier.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/message_center_impl.cc
[delete] https://crrev.com/bfca61a66e1d8decd8d3f2b798b7337c78226018/ui/message_center/message_center_switches.h
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/public/cpp/BUILD.gn
[add] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/public/cpp/features.cc
[add] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/public/cpp/features.h
[delete] https://crrev.com/bfca61a66e1d8decd8d3f2b798b7337c78226018/ui/message_center/public/cpp/message_center_switches.cc
[delete] https://crrev.com/bfca61a66e1d8decd8d3f2b798b7337c78226018/ui/message_center/public/cpp/message_center_switches.h
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/views/message_popup_collection.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/views/message_view.cc
[modify] https://crrev.com/bda6c8ffc35720750a7ab02ca7d2b2a0bc4878e2/ui/message_center/views/message_view_factory.cc