For years, Ubuntu and Firefox have strolled the open source countryside hand-in-hand. That could change with the release of Ubuntu 13.10, however, as Canonical is thinking about dumping Firefox for Chromium.It’s hard to believe that Firefox’s run as the default browser on Ubuntu could be coming to an end. In 2005, it was Firefox 1.0.2 that shipped with Hoary Hedgehog. Eight years later, you’ll find Firefox 20 in Ubuntu 13.04. When 13.10 arrives in the second half of this year, you may have to install the package manually from the Ubuntu Software Center if you want to keep surfing with the ‘fox.Lately there’s been a lot of heated discussion amongst Ubuntu developers about making the switch, and the pro-Chromium camp may very well win out. As you’d expect, Chromium’s rise in popularity (which is owed to the success of Google Chrome) is a consideration. It’s now the second biggest or biggest browser base in the world, depending on whose numbers you go by.But Firefox’s slide to number three isn’t the only reason Canonical is considering a switch. Performance is also a factor, as is Chromium’s ability to run Unity web apps in totally Chromeless windows — allowing for seamless integration with the Ubuntu desktop. There are also Canonical’s mobile ambitions to consider. Ubuntu Touch will be arriving soon, and it will be important for the desktop and mobile platforms to share as much code as possible — and to offer a familiar user experience. Switching to Chromium and the WebKit Blink engine would help keep things consistent.In the end, this might be the most critical issue. Popularity is important, sure, but Firefox is still one of the most widely-used and recognizable open source apps around. Mozilla has also been working its tail off to get performance back up to Chrome-like levels, and that’s been very apparent in recent releases.Canonical will be seeking input from the community before making a final decision, but Mark Shuttleworth has already made it clear that the community doesn’t hold the reins. If Canonical ultimately decides it’s time to make the switch to Chromium, no amount of discussion will change its mind.