Multiple HTTP connections accessing one session

Trying to fix the WPT WebDriver client behaviour, I've realised this isn't clearly specified anywhere.

Relatedly: https://github.com/w3c/webdriver-bidi/issues/47

A remote end has a list of active sessions.

When a connection is established, and the URL contains a session ID, it is looked up in the list of active sessions, per the processing model.

The only occasions when we remove something from the list of active sessions is in close the session.

This gets invoked only from Delete Session and Close Window.

Given the list of active sessions isn't local to the connection (and can't be, given we want to forbid multiple sessions with a single endpoint), this implies you can have multiple connections dealing with the same active session, modulo "the exact details of how this connection works and how it is established are out of scope".

This leeway I think can be used to justify disallowing multiple simultaneous HTTP connections (i.e., it is valid for the connection can only accept one socket at a time).

But I don't think that forbids making two sequential connections; https://github.com/web-platform-tests/wpt/pull/62028 seems to imply that everyone already allows this.

Start with the processing model and the active sessions definition, then read the close the session, Delete Session, and Close Window sections. Compare the expected behavior with web-platform-tests PR 62028 and the related WebDriver BiDi issue. Done means the specification clearly states whether sequential or simultaneous HTTP connections may access one session.