XHR prevents images to be downloaded in iOS6+ Safari/UIWebView

Please give your reaction at https://discussions.apple.com/message/20131649.

WHAT IS HAPPENING HERE:

This page demonstrates how the Safari/UIWebView browser on iOS 6 or higher is unable to download images while an XHR request is running. 

The script will add an image to the DOM (at t=2), then start an XHR request which will take 20 seconds to complete (t=3). 

While the request is running, a second image is added to the DOM (at t=7). 

In every browser we see that the image is downloaded and displayed immediately. In iOS 6+ Safari/UIWebView however, the image is only not downloaded until the XHR request is completed.


Note: If the images where downloaded from another host/port than the XHR request, this problem does not occur.

See this page source code for details on what is happening. The XHR request loads sleep.php with the following contents:

<?php
sleep($_GET['time'] * 1);
echo "OK";
?>