Worker constructor specification doesn't match browser behaviour for cross-origin URLs

[jdm]

What is the issue with the HTML Standard?

Testcase, running from a local http server on port 8000:

<script>
const urls = [
  "http://localhost:8001/worker.js",
  "https://example.com/worker.js",
  "file:///tmp/worker.js",
  "chrome://worker.js",
];
for (const url of urls) {
  try {
    let w = new Worker(url);
    w.onerror = (e) => console.log(url + ": asynchronous exception", e);
  } catch(e) {
    console.log(url + ": synchronous exception", e);
  }
}
</script>

Firefox:

chrome://worker.js: synchronous exception
http://localhost:8001/worker.js: asynchronous exception
https://example.com/worker.js: asynchronous exception
file:///tmp/worker.js: asynchronous exception

Chrome & Safari:

http://localhost:8001/worker.js: synchronous exception
w.html:13 https://example.com/worker.js: synchronous exception
w.html:13 file:///tmp/worker.js: synchronous exception
w.html:13 chrome://worker.js: synchronous exception

Servo (per the specification):

chrome://worker.js: asynchronous exception
https://example.com/worker.js: asynchronous exception
file:///tmp/worker.js: asynchronous exception
http://localhost:8001/worker.js: asynchronous exception

This is supposedly tested by https://github.com/web-platform-tests/wpt/blob/a94b364692b80c5cc02634dcb7e4935c76d0ebd7/workers/constructors/Worker/same-origin.html, but I can't figure out why Chrome is reported as failing the tests while Safari apparently passes them. However, when I run the tests in Safari on wpt.live, the expected tests fail just like Chrome.

Firefox's behaviour was pointed out in #2289 (comment), but nobody investigated other browsers as far as I can tell.

This came up because I noticed that sfgate.com creates a worker with chrome://juggler/content (why? who can say?) and other browsers behaved differently than Servo handling that.