GitLab

This CL adds a lacros browser test that creates a lacros window,
triggers overview mode, and then closes the window while overview mode
is still active.

Change-Id: Ib16b9f8dedabc49a3f1722bd6416f9c99ec7a8fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601260
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840317}