As you can probably infer from the length of the title, this is a bit of an edge case. Basically, among the notification issues I fixed were

(1) preventing an existing user from seeing the 'new user' notification when they forget their existing host on a new Chromebook and
(2) changing the logic of the 'Chromebook added' and 'host switched' events so that they only take into account verified hosts.

The solution to (1) was to check if the Chromebook had ever shown the 'Chromebook added' notification before and the solution to (2) was to make the host status restriction for the 'Chromebook added' and 'host switched' events more rigorous (i.e. require 'verified' instead of 'set).

As a result one case fell through the cracks:
1) User sets up host on Chromebook A.
2) Host is successfully set but not yet verified.
3) Host logs into new Chromebook B.
4) Host is verified.
5) User forgets host.
N note that when the user first logged into Chromebook B, they had a host that was set but NOT verified so they did not receive the 'Chromebook added' notification since it now requires a verified host.

The simplest solution is just to have the host_device_timestamp_recorder keep track of if a host has ever been set and replace the check for a previously shown 'Chromebook added' event with a check for a 'had a set host' timestamp.