(Maybe bug) service worker processes stay open after last tab is closed

Steps to reproduce:

1. Visit a site that uses a service worker (for example reddit.com)
2. Notice that in the CPU tab of Activity Monitor, a new process appears - "Orion Service Worker (reddit.com)"
3. Close the reddit tab.
4. Wait several minutes.
5. Note that the service worker process is still open and running.
6. Visit some other sites that use a service worker (e.g. caddy.community) and the same is true.
7. After a period of time, a number of service workers will be left running, for now-closed sites.

Expected behavior:
I am guessing that these old service workers should be closed after the last tab is closed, or shortly thereafter. Since they don't seem to be purged, I guess these will slowly use up 12 MB (approx) each, until you do a clean close/reopen of Orion.

Version 0.99.109.1.3-beta (WebKit 613.1.12)