Login: Tracks "signed_in" event isn't fired with Google logins

[rachelmcr]

Expected behavior

I expect that any time a user signs in to the app, the signed_in event will be fired. This is a critical event for analytics; we assume it is fired every time there is a successful login.

Actual behavior

When a user logs in with Google, the signed_in event isn't fired. Other events (including the social login success event) do fire as expected, and signed_in is fired as expected in other login scenarios, including social login with Apple.

Steps to reproduce the behavior

1. Start logged out of the app, ready to log in to a WordPress.com account that either has Google connected or is using your Google email address (not a8c).
2. Select "Log in" and continue with Google.
3. Log in to your Google account when prompted.
4. Confirm you end up logged in to the app.
5. Check the analytics events that were fired, and note that signed_in was not fired.

Tested on [iPhone XS], iOS [13.1.3], WPiOS [13.4.1]