GitLab

Use NotificationDisplayService instead of MessageCenter in tests.

Bug: 783018
Change-Id: I2bc849e90f5f899144d015c83755f8eade62e185
Reviewed-on: https://chromium-review.googlesource.com/867291
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530411}