The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/331bfdfc79d5ff8fc244190c12cac0fdbc0eee70

commit 331bfdfc79d5ff8fc244190c12cac0fdbc0eee70
Author: Elliot Glaysher <erg@chromium.org>
Date: Wed Sep 27 17:22:29 2017

[ash] Make chrome's immersive mode watch properties.

Instead of implementing an ash specific observer type, watch shared
properties on the aura::Window instead. This removes dependence on
non-public ash types, and simplifies all three ashs (classic,mus,mash)
so they go through the same code path.

Bug:  640381 
Change-Id: I1837202ae3fadd177c2a54b31d6cc31ed974b621
Test: ImmersiveModeControllerAshTest.*, Manual in all 3 configurations
Reviewed-on: https://chromium-review.googlesource.com/685538
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Elliot Glaysher <erg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504716}
[modify] https://crrev.com/331bfdfc79d5ff8fc244190c12cac0fdbc0eee70/chrome/browser/ui/views/frame/immersive_mode_controller_ash.cc
[modify] https://crrev.com/331bfdfc79d5ff8fc244190c12cac0fdbc0eee70/chrome/browser/ui/views/frame/immersive_mode_controller_ash.h