[chris_st]

I think the line:

> It's a JavaScript Worker, so it can't access the DOM directly. Instead, a service worker can communicate with the pages it controls by responding to messages sent via the postMessage interface, and those pages can manipulate the DOM if needed.

gives me some hope that it's intended to be isolated from all other tabs (including the one that started it!).

There will be bugs, of course, but it looks to me like they're starting from a secure position, which gives me hope.