The point here is to have a URL which allows us to set a domain cookie, and which doesn't cause `PHPUnit_Extensions_SeleniumCommon_RemoteCoverage` to throw an Exception when it tries to parse the content.

Ideally, we would use `/php/get_coverage.php` as URL and write a small script that works pretty much like `SeleniumCommon/phpunit_coverage.php` (i.e. it doesn't do anything if no cookie is set, and outputs the coverage info if it is). However, since we can't run PHP 5.4's built-in server (instead of `python -m SimpleHTTPServer`), that doesn't work. As a little hack, we could use `/coverage/dummy.txt`, but Firefox pops up a download dialog and doesn't allow us to set a cookie (it complains that it's not an an HTML page).

As a nasty solution, we use this dummy URL. No server is listening on that port, and Firefox displays an error message, but magically still allows us to set a cookie! We really shouldn't depend on that behavior, but I don't see a way around it for now.