The `req.origin` property on the `PayloadRequest` object does not
include the port when running on localhost, a requirement of the [HTML
Living Standard](https://html.spec.whatwg.org/#origin). This was because
we were initializing the url with a fallback of `http://localhost` (no
port). When constructed via `new URL()`, the port is unable to be
extracted. This is fixed by using the `host` property off the headers
object, if it exists, which includes the port.
Partial fix for #11448.
a65289c211