[DL] Update layout tests to be mode 2 tests.

This updates the layout test and some code changes to make those tests
pass to be mode 2 tests (ie append after lock).


Bug: 882663
Change-Id: I44554d486c5af0db1c680d5be719d687fd2745d2
Reviewed-on: https://chromium-review.googlesource.com/c/1344263
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611264}
50 files changed