The printer is a Brother HL-2280-DW connected as 192.168.1.25. I can ping it, so the connection is good. I can print to it from any computer and from any program except Chromium. When I print from Chromium I look at the GUI print queue for the printer, and no print jobs appear. In other words, the problem is that Chromium is not even sending the print job. A print job appears in the queue when I print from anything else.
I've poked all over Chromium's settings looking for some permissions or restrictions issue, but I can't find anything. And Chromium obviously has no problem accessing the network. It's just printing that doesn't work. And I mean that it won't print from any web page. If I copy the URL of a Chromium web page and paste it into Firefox, then the page prints fine. Why would Chromium refuse to print?