Isolated Script API

Hi all,

For the Houdini APIs which extend the rendering pipeline, we believe that
we'll need an isolated execution environment for these APIs to be exposed
in.

For example, the CSS Paint API (
https://drafts.css-houdini.org/css-paint-api/) allows authors to hook into
the paint phase of rendering. We don't think that it would be good for the
web platform to allow full DOM, network, etc access during paint, because:
 - Allows potential performance foot-guns.
 - Doesn't lead to a rational platform.
 - Doesn't allow performance optimizations on behalf of UAs.

I've written down some initial thoughts here:
http://bfgeek.com/css-houdini-drafts/css-script-api/Overview.html

In this spec I haven't written down where all the other APIs would be
exposed so use your imagination.

As always, let me know of your thoughts!

Thanks,
Ian