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Since https://crrev.com/c/2044644, the desk bar is an activatable
window placed in the active desk's container. Removing the active
desk from overview means hiding its container, and showing another
one. The desk bar should be one of those windows that move to the
newly-activated desk's container when its original (previously-active)
desk is removed.

BUG=1053771
TEST=Manually, expanded an existing test.

Change-Id: Id4bb2084ac0117fab4334819c9d79e40e8a565d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2063810Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742793}