AFAICT there is no way to set this on a Chromebook though - and since Chrome is embedded into the OS using Firefox is really painful in comparison. I guess I will have to use uBO Lite.
edit: There is apparently a way to set it by enabling Developer Mode, but Developer Mode is itself really annoying - it shows a popup screen every boot.
edit: There is apparently a way to set it by enabling Developer Mode, but Developer Mode is itself really annoying - it shows a popup screen every boot.