[floil]

The three data sources you mention are kept in the browser process (which is the privileged singleton process that spawns the sandboxed child processes that actually parse and execute web content). However the child processes can query and mutate them (to support e.g document.cookie). Those JS apis do work in iframes. In your example, we would create a facebook.com subframe process separate from the foo.com process for the main document.

You can see your example in action by enabling site isolation, visiting a page with a FB like button, and opening Chrome's task manager. You can even kill the subframe process, and it shouldn't take down the whole tab.