Simplify GC model

[marcoscaceres]

closes #266

The following tasks have been completed:

• Modified Web platform tests

Implementation commitment:

• WebKit (https://bugs.webkit.org/show_bug.cgi?id=236349)
• Blink (link to issue)
• Gecko (https://bugzilla.mozilla.org/show_bug.cgi?id=1754372)

---

Preview | Diff

[marcoscaceres]

Added test: web-platform-tests/wpt#30189

Checking manually with the code below, this doesn't appear to be implemented in WebKit or Gecko (but works fine in Chrome).

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

[marcoscaceres]

Filed bugs for Gecko and WebKit...

[marcoscaceres]

I’ll see if I can patch Gecko.

[miketaylr]

LGTM