Browser loops on connectivity problems

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Configure a SQUID proxy
2. Access shellinabox going through the SQUID proxy
3. Connect to remote host in your browser and login
4. Kill your SQUID proxy

What is the expected output? What do you see instead?
I would expect the browser to disconnect or retry gracefully every X secs 
(polling or similar).
What I see instead is the browser freezing because of a continuous loop of POST 
requests failing. I a not able to use the browser anymore and my computer is 
overloaded.

What version of the product are you using? On what operating system?
Latest and greatest from HEAD (v2.13-2-gea1937a)

Please provide any additional information below.
The problem could just be in the pending POST that is always left opened and 
may hijack the SQUID proxy threads (it is like a page requests that never ends 
and will eventually time-out). Apart from the UX behaviour that is not nice, 
the HTTP Proxy gets overloaded as well.

Original issue reported on code.google.com by [email protected] on 6 Jan 2015 at 11:56