GitLab

This routes changes to MultiUserWindowManager that impact mus windows over
a mojom. This way the ash side can map these windows appropriately.

BUG=756085,875111
TEST=covered by test

Change-Id: Ie69732f290d919e591505234669328e69cc4afc9
Reviewed-on: https://chromium-review.googlesource.com/c/1330719
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609338}