Comment 12 for bug 1729558

Ok Turns out Java has some super funky code:

        int componentState = context.getComponentState();
        if ((componentState & SynthConstants.DISABLED) ==
                              SynthConstants.DISABLED){
            if (!GTKLookAndFeel.is3()) {
                Color orgColor = g.getColor();
                g.setColor(context.getStyle().getColor(context,
                        GTKColorType.WHITE));
                x += 1;
                y += 1;
                super.paintText(context, g, text, x, y, mnemonicIndex);

                g.setColor(orgColor);
                x -= 1;
                y -= 1;
            }
            super.paintText(context, g, text, x, y, mnemonicIndex);
        }

Removing this silly +1 white shadowing nonsense results in perfect looking menus both when dark and light.
I will take this upstream and see if it can be patched into Ubuntu, not a theming bug after all.