GitLab

https://crrev.com/c/2318888 added a "GetOriginalProfile" call to fix a
crash in incognito. Unfortunally that introduced a new crash for Guest
sessions. GetOriginalProfile() returns something that crashes when
trying to open a browser - see https://crbug.com/1121553. Add a new
method to AppService to handle the profile redirects correctly and in a
single place.

Also adds more tests.

Bug: 1122480
Change-Id: I63e3d2766d61b416d1e7590bc67a937b817848ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2381230Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Rachel Carpenter <carpenterr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803399}