What happens if ...?

When do we get an unsubscription event from Google?

Clearing Cookies and other site and plugin data after subscribing, and sending another message

Environment: Chrome 54.0.2840.87 (64-bit) on Mac OS X 10.11.6

Revision: c5ec6c5a12f2ed748bb08c1a8567b3c0df89dccd-refs/branch-heads/2840@{#805}

1. Subscribe.
2. Close the tab you subscribed on.
3. Clear Cookies and other site and plugin data (Settings -> Privacy -> Clear Browsing Data...).
4. Send yourself a notification.
5. Observe delivery results are okay.
6. Send yourself another notification.
7. Observe delivery results mark you as unsubscribed.

Do we get a unsubscription event right after the first message delivery?

No. It looks like the browser sends an unregistration message though:

Do we get an unsubscription event right after the second message delivery?

Yes. Google immediately tells us the user is no longer subscribed. The browser's chrome://gcm-internals does not record any message received.

Note 1: It looks like clearing Cookies and other site and plugin data is the only setting necessary in clearing browser data to unsubscribe the user (all the other clearing options are unrelated).

Note 2: This method of clearing data also unregisters the service worker itself which means the entry in chrome://serviceworker-internals is missing.