title: Ajax File download Issue
body: <p>I am downloading a dynamic file in my application, simulating ajax using iframes. What I am doing is, when the download request is made, I will create a dynamic invisible iframe, and set the src of  my iframe as the download url.I am able to successfully download the file, but the requirement is to show a download indicator once the download starts and that should finish as soon as the download dialog comes up.I provided call back after iframe creation to show the download indicator, which is successfully working, and provided another method on the 'onload' of the iframe, expecting it will be invoked, when the download dialog comes up. But unfortunately, that is not working, and because of that even after the download completes, my progress indicator is still there. I am not able to remove that. Then I came to realize that the since the content type of the response is not html, it will be served by a separate process, which leads to the download dialog and because of that my onload method is never getting called. Please let me know a solution for this.</p>