Why doesn’t Chrome see my CSS files in it’s Coverage tab on my local development environment?

I’ve got a vagrant environment where I do some Drupal 7 development and I wanted to remove some unused CSS. So, I hit the record button and started loading pages. JavaScript files were picked up fine. And so were some external CSS files. But, it would not find any CSS.

I thought perhaps it was because of Drupal 7’s practice of adding a query string to the end of its CSS and JS files, so I stopped Drupal from doing that. But still, it’s not finding the CSS files. Any ideas why it wouldn’t?