[giow] (2) Since this made it likely that overloaded servers would just get even more overloaded, pull back a little and let all 5xx errors stop EventSource reconnects. It still reconnects if the connection drops, though. (Compat: 5xxs don't cause reconnects in deployed browsers currently as far as I can tell.)
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@7634 340c8d12-0b0e-0410-8428-c7bf67bfef74