gecko-dev/netwerk/test/mochitests/user_agent.sjs

function handleRequest(request, response)
{
    // avoid confusing cache behaviors
    response.setHeader("Cache-Control", "no-cache", false);
    response.setHeader("Content-Type", "text/plain", false);
    response.setHeader("Access-Control-Allow-Origin", "*", false);

    // used by test_user_agent tests
    response.write(request.getHeader('User-Agent'));
}