FileReference disabled on Chromebooks?

I have a client testing a Flash web application on his Chromebook which is supposed to include functionality for saving files to your computer. Files are saved using the save() method of FileReference. This works fine in all browsers on Windows and Mac desktops, and used to work on the client's Chromebook. However, recently, when he presses the 'Save' button which triggers the FileReference, nothing happens - no dialog appears, nor any error message.

I don't have a Chromebook on hand to test this; I've tried walking the client through various plugin and security settings on his Chromebook, but haven't had any luck finding an underlying cause so far. Has Google disabled support for saving via FileReference in ChromeOS or through the browser?

He's using Chrome Version 60.0.3112.80 (Official Build) (64-bit)