title: how to update accept property in request header of form.submit in extjs
body: <p>When I upload some file through extjs form.submit() my <code>accept</code> and <code>content type</code> in request header looks like this</p>
  
  <pre><code>Accept : application/x-ms-application, image/jpeg, application/xaml+xml, image/gif, image/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*
  Accept-Language : en-US
  Content-Type : multipart/form-data; boundary=---------------------------7df13e2a2600578
  </code></pre>
  
  <p>and in response I am getting <code>content type: application/json</code></p>
  
  <p>Now IE 11 treat response as json file and always ask to download <code>.json</code> file.</p>
  
  <p>We are using REST controllers at java level.</p>
  
  <p>Note: This issue cannot be reproduced on all IE 11(on some IE11 it is working fine)</p>
  
  <p>I tried to change header content in extjs but no luck.</p>
  
  <p>Here is my code</p>
  
  <pre><code>form.submit({
  headers: {
      'accept':'application/json',
      'contentType': "application/x-www-form-urlencoded;charset=utf-8"
  },
                  url: 'http://dummyurl/abc/rest/xyz/update',
                  success: function(fp, o) {
                                         .
                                         .
                                         .
  </code></pre>
  
  <p>Response: </p>
  
  <pre><code>{"statusCode":"200",'records':null, 'success':true, 'message':'Success'}
  </code></pre>
  
  <p>Response Header: </p>
  
  <pre><code>Content-encoding:gzip
  Content-language:en-US
  Content-type:application/json
  Date:Tue, 11 Aug 2015 12:29:46 GMT
  Transfer-encoding:chunked
  Vary:accept-encoding
  </code></pre>
  
  <p>Can anybody please guide me how to change request header in form.submit() ? </p>