35393df8e1
This isn't particularly big but it has lived in BrowserGlue for a surprisingly long time, and doesn't really belong there. There wasn't a _great_ home for this, so I created a new directory. SitePermissions.sys.mjs and other bits probably want to live in this directory too, but one thing at a time. Differential Revision: https://phabricator.services.mozilla.com/D244424