Hello,
I just finished installing my new test server, for the development necessities is a Windows 2012 r2 x64 server with IIS 8.5 and php 5.3, 5.4, 5.5 and 5.6.
I have configure the uploadprogress.dll obtained following the instructions of this topic (https://www.drupal.org/node/1686816) and phpinfo detect if fine but drupal 8 do not detect it, am I missing something?

Cannot understand why the uploadprogress is only supported in apache servers according to the documentation.

Thanks!