The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/64bbb2cf3aa33913002f90ee453c47029b0185f9

commit 64bbb2cf3aa33913002f90ee453c47029b0185f9
Author: rjkroege <rjkroege@chromium.org>
Date: Tue May 24 19:13:54 2016

Fix mus_demo

mus_demo was using the CreateWindowTreeHost to obtain a root window.
This interface is intentionally not available on CrOS devices where the
idea of a WindowTreeHost as the container for a PlatformWindow does not
apply. Switch mus_demo to being a WindowManager implementation so that
it works on all mus targets.

BUG= 611504 

Review-Url: https://codereview.chromium.org/2005143002
Cr-Commit-Position: refs/heads/master@{#395670}

[modify] https://crrev.com/64bbb2cf3aa33913002f90ee453c47029b0185f9/components/mus/demo/manifest.json
[modify] https://crrev.com/64bbb2cf3aa33913002f90ee453c47029b0185f9/components/mus/demo/mus_demo.cc
[modify] https://crrev.com/64bbb2cf3aa33913002f90ee453c47029b0185f9/components/mus/demo/mus_demo.h