setting this up so we're always polling is a little complicated, but we can cheat and just do one quick poll right before trying to use the connection.

related to this; we need to make sure that we always open a new connection when sending a non-idempotent request (eg, POST), because if we get a network error after writing the request, we won't know whether or not the server actually processed it or not. (And so we want to minimize the possibility of getting a network error, and so we don't want to use a cached-and-possibly-timed-out connection.) Apparently this is what other browsers do (qv http://www.ietf.org/mail-archive/web/hybi/current/msg00391.html).

updating summary to reflect remaining part of the bug

fixed the remaining part (and re-fixed the earlier part to work with
Windows too)