Were you able to solve this? I would like to do the same thing.
I have the file downloading properly but the 'Download Complete" dialog with the option to open the file does not appear as in typical browser behavior.
Please let me know.
Actually, I stopped working on this task and did not solve this in this manner.
Thank you for responding.
I also gave up on using FileReference.browse() and instead used NavigateToURL() , with "blank", which resulted in the browser's default save/open dialog, which is what we wanted.