GitLab

This effectively disables the feature in tablet mode if entered before
creating more than one desk.

BUG=976442
TEST=Manual, added a new test.

Change-Id: I38966dd59cf0eb76873958ca0fb4472c9bf5a53f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1666548
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670347}