Implement Document.open() and Document.close()

[jdm]

Blocks #13942.

Spec: https://html.spec.whatwg.org/multipage/webappapis.html#dom-document-open, https://html.spec.whatwg.org/multipage/webappapis.html#dom-document-close

[dpyro]

I will give this a go. Would this be the place to go? https://github.com/servo/servo/blob/master/components/script/dom/document.rs

[dpyro]

Cancelling my go based on @KiChjang’s advice.

[jdm]

This also hits us on Google Maps.

[nox]

Should we implement window.open at the same time? I feel like implementing only the version of document.open that takes 2 arguments will break other sites trying to call the 3 arguments version.

[jdm]

Pragmatically, I don't think it makes sense to try to solve the issues with window.open at the same time.

[jdm]

Those sites that use the three argument version are already broken by it not existing, so I don't think the effect will be any worse.

[Ms2ger]

We can add the 3-argument overload and unconditionally throw on the Rust side; that's probably better than WebIDL's default of ignoring stray arguments.

[nox]

Seems like my job suddenly became easier to do: whatwg/html#1698