32547d2eff
GTK+ doesn't support shading of client-side decorated windows, and likely never will (not least because shading is conceptually questionable if the app customizes the titlebar), and neither do other CSD implementations like Chromium's. A shortcut that only works with a decreasing number of windows is more confusing than helpful, so don't expose it. https://bugzilla.gnome.org/show_bug.cgi?id=645460
