GitLab

When we reach one third of work area, stop shrinking the overview bounds
and instead start sliding it out off screen.

Test: added test
Bug: 872141
Change-Id: I4d42e5943485c9a4d96205d1a1870823305b49e9
Reviewed-on: https://chromium-review.googlesource.com/1169974
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581995}