title: Catch too long form submission
body: <p>I am developing an HTML page which has simple HTML form (nothing special) being submitted by button. There is a couple of situations when form submitted and response comes too long (if whenever really comes back). How can i organize the form the way it fires some callback when waiting a response is too long? We could show up some notice for user, indicating our server is overloaded in that situation. </p>
  
  <p>Here is request that being sent by form:</p>
  
  <pre><code>POST http://example.com/search HTTP/1.1
  Host: example.com
  Proxy-Connection: keep-alive
  Content-Length: 83
  Cache-Control: max-age=0
  Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
  Origin: http://example.com
  Upgrade-Insecure-Requests: 1
  User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36
  Content-Type: application/x-www-form-urlencoded
  Referer: http://example.com/
  Accept-Encoding: gzip, deflate
  Accept-Language: ru-RU,ru;q=0.8,en-US;q=0.6,en;q=0.4
  Cookie: [cookie definition omitted]
  
  [form data omitted]
  </code></pre>
  
  <p>Is <code>Proxy-Connection: keep-alive</code> influence the process somehow? Googling led me to <a href="https://github.com/caxap/jquery-safeform">https://github.com/caxap/jquery-safeform</a> plugin, but it is for a little bit different purpose.</p>