Permission API: PermissionStatus with registered "change" listeners shouldn't be GC'd

[Marcos Caceres]

Related spec change:
https://github.com/w3c/permissions/pull/360

It should be possible to get a PermissionStatus object, register a listener on it, and allow it to go out of scope (but not have it GC'd) 

For example: 

```JS
(async () => {
  const perm = await navigator.permissions.query({ name: "geolocation" });
  perm.onchange = () => { console.log("pass") };
  console.log("going out of scope");
  // bye bye perm
})();

// prompts for permission
navigator.geolocation.getCurrentPosition(console.log);
```

Changing the permission of Geolocation in the above should produce "pass" in the developer console.

[Marcos Caceres]

Noting the works in Blink-based browsers.

[youenn fablet]

Right, we do not support yet onchange event handler but when it is the case, we should definitely do something about it.

[Radar WebKit Bug Importer]

<rdar://problem/88969778>