[DL]: Add an acquire-update-disconnect-commit test.

This patch adds a test that does an acquire and update, then
before the update finishes it removes the element from the DOM and does
a commit. This fails the update promise.

This test is meant to be paired with another one already checked in
where we don't call a commit and also expect the update to fail.

R=chrishtr@chromium.org

Bug: 882663
Change-Id: Idbe58b5162d4189da05379ed2044a0e620ce5dd9
Reviewed-on: https://chromium-review.googlesource.com/c/1393451
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619669}
2 files changed