On new accounts, we can accelerate the process of setting up security
by explicitly checking (at the end of the security process). The user
is not required to "answer" the asynchronous notification.
This is an imperfect solution, as a slow initial sync could leave the
user in a non-synced Inbox (with a notification waiting for them), but
we can come back to this after we evaluate real-world performance.
Bug: 2387961
d71d0b223a