You can now apply the mobile skin to the desktop site [1]. Wahhhh?! To cut a long story short, to help MobileFrontend and VisualEditor integrate nicely with one another, we needed the mobile skin to be registered as a valid skin. We've previously avoided this as we didn't want to surface this in the Special:Preferences (a side effect of doing so). Kaldari however found a way we can supress it there, so thus we went and registered it [1].
I encourage editors to check how their stuff looks in the minerva skin on a small window size. This should make mobile optimisation a lot easier for you! :)
[1] http://en.wikipedia.beta.wmflabs.org/wiki/Forty-seven_Ronin?useskin=minerva [2] https://gerrit.wikimedia.org/r/#/c/118037/