Chromium: Prevent assistant on Guest Logins.

When performing a guest login IdentityManagerFactory can return a null
pointer.

Bug: 951416
Change-Id: I279d98d03892643e288cbaf107247938b00530db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574266
Commit-Queue: Brian Geffon <bgeffon@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652950}
1 file changed