The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/43a605ba0c3acb7ec10a68ab1e4105ddde8288d2

commit 43a605ba0c3acb7ec10a68ab1e4105ddde8288d2
Author: Ahmed Fakhry <afakhry@chromium.org>
Date: Wed Oct 31 23:03:24 2018

Overview: Minor cleanup

In preparation for the VDs work, I noticed some code we
can simplify, or needed only for DCHECK, which turned out
we can remove completely.

BUG=866622

Change-Id: I676194493d263213c0fdd621134dda4efabc408d
Reviewed-on: https://chromium-review.googlesource.com/c/1303354
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604432}
[modify] https://crrev.com/43a605ba0c3acb7ec10a68ab1e4105ddde8288d2/ash/wm/overview/window_grid.cc
[modify] https://crrev.com/43a605ba0c3acb7ec10a68ab1e4105ddde8288d2/ash/wm/overview/window_selector.cc
[modify] https://crrev.com/43a605ba0c3acb7ec10a68ab1e4105ddde8288d2/ash/wm/overview/window_selector.h