Tests that downloads are correctly identified when intercepting navigation responses.
Regular navigation: 
Intercepted http://127.0.0.1:8000/devtools/network/resources/resource.php
Download via content-disposition: 
Intercepted http://127.0.0.1:8000/devtools/network/resources/resource.php?download=1
Download via unhandled MIME type: 
Intercepted http://127.0.0.1:8000/devtools/network/resources/resource.php?mime_type=application/octet-stream
Now downloading by clicking a link: 
Intercepted http://127.0.0.1:8000/devtools/network/resources/resource.php