This refers to the ScreenMus in ash, not the views one.

Here's what is left: IsWindowUnderCursor() and GetWindowAtScreenPoint().

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/860df320f00a381f2a743d14a7fc095130428255

commit 860df320f00a381f2a743d14a7fc095130428255
Author: erg <erg@chromium.org>
Date: Thu Mar 02 00:16:17 2017

mus+ash: Copy parts of ScreenAsh to ScreenMus.

This copies the implementation of ScreenAsh::IsWindowUnderCursor() and
ScreenAsh::GetWindowAtScreenPoint() to ScreenMus; the rest can't be
consolidated because of usage of the display manager, which is mostly
unimplemented on mus+ash.

BUG= 671408 

Review-Url: https://codereview.chromium.org/2726603003
Cr-Commit-Position: refs/heads/master@{#454113}

[modify] https://crrev.com/860df320f00a381f2a743d14a7fc095130428255/ash/mus/BUILD.gn
[modify] https://crrev.com/860df320f00a381f2a743d14a7fc095130428255/ash/mus/screen_mus.cc
[modify] https://crrev.com/860df320f00a381f2a743d14a7fc095130428255/ash/mus/screen_mus.h
[add] https://crrev.com/860df320f00a381f2a743d14a7fc095130428255/ash/mus/screen_mus_unittest.cc

 Issue 602727  has been merged into this issue.