title: HTTP Header Content-Length not work
body: <p>I wish to display the size of the file to the client when they download it.<br />
  But HTTP Header Content-Length not work.<br />
  My Environment is follow.</p>
  
  <ul>
  <li>Apache 2.2</li>
  <li>mod_deflate</li>
  <li>Rails3.2</li>
  </ul>
  
  <p>A download file is in the rails project public folder.</p>
  
  <p>Response Header is this when I download it.</p>
  
  <blockquote>
    <p>Accept-Ranges bytes<br />
    Access-Control-Allow-Head...    origin, x-requested-with, content-type<br />
    Access-Control-Allow-Meth...    PUT, GET, POST, DELETE, OPTIONS<br />
    Access-Control-Allow-Orig...    http://<strong>*</strong>.com<br />
    Connection  Keep-Alive<br />
    Content-Encoding    gzip<br />
    Content-Type    application/octet-stream<br />
    Date    Fri, 14 Dec 2012 05:15:09 GMT<br />
    Etag    "c1bcc-1c828800-4d0a3ac0f7389"<br />
    Keep-Alive  timeout=5, max=100<br />
    Last-Modified   Wed, 12 Dec 2012 08:34:51 GMT<br />
    Server  Apache<br />
    Transfer-Encoding   chunked<br />
    Vary    Accept-Encoding<br /></p>
  </blockquote>
  
  <p>Is there any way to display the Content-Length?</p>