GitLab

We need to distinguish between MultiProcessMash, SingleProcessMash and
both (aka IsUsingWindowService). Clean up some usage in login and
accessibility.

Bug: 874468
Change-Id: Ibf9694f45114491bf54b232a906b6a5a390e3f05
Reviewed-on: https://chromium-review.googlesource.com/1180344
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584613}