The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e66472c74362d95c503867eea4267772d8505cf5

commit e66472c74362d95c503867eea4267772d8505cf5
Author: Leonard Grey <lgrey@chromium.org>
Date: Tue Oct 16 16:19:49 2018

Add method to query system dark mode status in NativeTheme

Bug: 850098, 893598
Change-Id: I0ec85e12ae0714974e4d8122914afe330ac0fe93
Reviewed-on: https://chromium-review.googlesource.com/c/1240172
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600008}
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/base/mac/sdk_forward_declarations.h
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/ui/native_theme/native_theme.cc
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/ui/native_theme/native_theme.h
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/ui/native_theme/native_theme_mac.h
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/ui/native_theme/native_theme_mac.mm
[modify] https://crrev.com/e66472c74362d95c503867eea4267772d8505cf5/ui/views/view_unittest.cc

Is there a tracking bug for Chrome OS dark mode yet?

+1 to question about CrOS dark mode bug. What is its priority for Q1?

It's not on the desktop team's radar. Maybe sgabriel@ has an idea?

Light/Dark mode on Chrome OS is still in its conceptual phase.
Currently the plan is to hold off on getting Chrome dark mode until we get a system switch.