+jamescook because this has to be done differently (than original delegate approach).

Actually it wasn't that long. looks like this CL removed ScreenOrientationDelegateChromeos from shell_content_state without adding it elsewhere? estade@, can you look into it?

https://chromium-review.googlesource.com/c/chromium/src/+/1107128

Is this an extension API? A JavaScript API?

It's JS api.

https://developer.mozilla.org/en-US/docs/Web/API/ScreenOrientation/lock

this is a decent demo page https://whatwebcando.today/screen-orientation.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f553d08df3754078e40fc5817eaf5dcd94da4b72

commit f553d08df3754078e40fc5817eaf5dcd94da4b72
Author: Evan Stade <estade@chromium.org>
Date: Mon Oct 01 20:02:18 2018

Chrome OS: restore screen orientation delegate for classic Ash.

Mash implementation is a TODO.

Test: put in tablet mode, go to [1], press Lock in Current Orienation

[1] https://whatwebcando.today/screen-orientation.html

Bug:  889981 
Change-Id: I19192a92ba927eba76c63089fa57c1288b34ff1c
Reviewed-on: https://chromium-review.googlesource.com/1252525
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595526}
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/ash/BUILD.gn
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/ash/content/display/DEPS
[rename] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/ash/content/display/screen_orientation_controller_unittest.cc
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/ash/DEPS
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/ash/chrome_browser_main_extra_parts_ash.cc
[modify] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/ash/chrome_browser_main_extra_parts_ash.h
[rename] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.cc
[rename] https://crrev.com/f553d08df3754078e40fc5817eaf5dcd94da4b72/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.h

Oshima-san, could you verify the fix on trunk before I request a merge?

Yes, it works on ToT. Thank you for promopt fix!

Merge request is late in the cycle but the fix seems important because it's addressing a regression in an html5 api.

This bug requires manual review: We are only 12 days from stable.
Please contact the milestone owner if you have questions.
Owners: benmason@(Android), kariahda@(iOS), geohsu@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f

commit bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f
Author: Evan Stade <estade@chromium.org>
Date: Wed Oct 03 19:33:23 2018

Chrome OS: restore screen orientation delegate for classic Ash.

Mash implementation is a TODO.

Test: put in tablet mode, go to [1], press Lock in Current Orienation

[1] https://whatwebcando.today/screen-orientation.html

Bug:  889981 
Change-Id: I19192a92ba927eba76c63089fa57c1288b34ff1c
Reviewed-on: https://chromium-review.googlesource.com/1252525
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#595526}(cherry picked from commit f553d08df3754078e40fc5817eaf5dcd94da4b72)
Reviewed-on: https://chromium-review.googlesource.com/c/1259494
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#842}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/ash/BUILD.gn
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/ash/content/display/DEPS
[rename] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/ash/content/display/screen_orientation_controller_unittest.cc
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/ash/DEPS
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/ash/chrome_browser_main_extra_parts_ash.cc
[modify] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/ash/chrome_browser_main_extra_parts_ash.h
[rename] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.cc
[rename] https://crrev.com/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.h

The following revision refers to this bug: 
https://chromium.googlesource.com/chromium/src.git/+/bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f

Commit: bc3d5cb5c0dc64568edb4d0e80c642c9bb41063f
Author: estade@chromium.org
Commiter: estade@chromium.org
Date: 2018-10-03 19:33:23 +0000 UTC

Chrome OS: restore screen orientation delegate for classic Ash.

Mash implementation is a TODO.

Test: put in tablet mode, go to [1], press Lock in Current Orienation

[1] https://whatwebcando.today/screen-orientation.html

Bug:  889981 
Change-Id: I19192a92ba927eba76c63089fa57c1288b34ff1c
Reviewed-on: https://chromium-review.googlesource.com/1252525
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#595526}(cherry picked from commit f553d08df3754078e40fc5817eaf5dcd94da4b72)
Reviewed-on: https://chromium-review.googlesource.com/c/1259494
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/branch-heads/3538@{#842}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f96e813b4cd956aaad1550d122a02ecd160c70b2

commit f96e813b4cd956aaad1550d122a02ecd160c70b2
Author: Evan Stade <estade@chromium.org>
Date: Thu Oct 18 18:55:38 2018

Mash: Implement ScreenOrientationDelegateChromeos

Test: put in tablet mode, go to [1], press Lock in Current Orientation

[1] https://whatwebcando.today/screen-orientation.html

Bug:  889981 
Change-Id: I2a4381b511c260a3845fbfd42a597cafe581fb43
Reviewed-on: https://chromium-review.googlesource.com/c/1250097
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600845}
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/display/screen_orientation_controller.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/display/screen_orientation_controller_test_api.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/public/interfaces/ash_window_manager.mojom
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/wm/splitview/split_view_divider.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/ws/ash_window_manager.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/ash/ws/ash_window_manager.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/browser/ui/ash/DEPS
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/browser/ui/ash/chrome_browser_main_extra_parts_ash.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/browser/ui/ash/screen_orientation_delegate_chromeos.h
[add] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/browser/ui/ash/screen_orientation_delegate_chromeos_browsertest.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/chrome/test/BUILD.gn
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/content/browser/screen_orientation/screen_orientation_provider.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/content/browser/screen_orientation/screen_orientation_provider.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/content/public/test/browser_test_utils.cc
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/content/public/test/browser_test_utils.h
[modify] https://crrev.com/f96e813b4cd956aaad1550d122a02ecd160c70b2/services/ws/window_tree.h