This is a pretty old bug, not from the last few months.
Note that this is not the place for general web development question, this group only discusses the Developer Tools feature.
For printing without a prompt, you can use --kiosk --kiosk-printing (it will open Chrome in full screen, though).
--disable-print-preview seems to still be supported. I am not sure why it does not work for you. For me, on Windows 7, it shows the system print dialog in response to window.print();.
Though it does not show up call window.close(); right away, right. This may or may not be a bug.
You can search
crbug.com for an existing issue and star it. If you cannot find one, file a new issue using the "New issue" link on the same page.
Please, do not add a "+1" or "Me too" or "Confirmed" (or similar) comment. It just wastes the time of Chrome engineers and sends unnecessary e-mails to all of the people who starred the issue.
You can reply with a link to the found or created issue and might get triaged (and fixed) faster.