Able to reproduce the issue on reported chrome version 69.0.3497.100 also on latest chrome 71.0.3558.0 using Mac 10.13.6 and Windows 10 and 7.  

Same behavior is seen on M60(60.0.3112.113) hence considering it as non-regression and marking it as Untriaged.

Note: .pdf extension seen on Ubuntu

Thanks..! 

Not sure if we should do this. 

I suppose it should. Since you have set the headers it should open it as pdf as the other browsers do! Only imho workaround is to explicitly define the extension in file name property I.e blanks.pdf

Can you provide a sample URL? I'm assuming the file opened did not have the .pdf extension already.

Note that if you open and save a .pdf file, even if the original file has the ".pdf" extension, the save dialog will not show it in Mac (I haven't checked in Windows) but the file will be saved with the extension. This is consistent with other file types in Chrome.

Also, this was marked as regression, but #3 says it's not. I'm confused. Let's get an example to get on the same page.

I do not have a public rest URL to expose. If you have any server (with java)  for test purposes I can upload the code.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Assigning to hnkakshima@, so he can follow up when he is back in the office.

In Mac, Chrome does not show the file extension when it is saving anything. Try saving an HTML page, or an image. I assume that's by design.

The extension is added to the actual file, though, if it was originally there. If a file with no extension is opened and saved, the extension is not added.

AFAICT, this is WAI.