[DL]: Add a test to ensure we can force true layout after commit().

This patch adds a test that verifies that forced layouts after a call
to commit() act as if there is no display lock and perform true layout.

Note that in this test we don't wait for the commit() promise completion.

R=chrishtr@chromium.org

Bug: 882663
Change-Id: I6aa6a17fbcb2b61e54cba4eed1e56ee59c404798
Reviewed-on: https://chromium-review.googlesource.com/c/1452496
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628834}
1 file changed