@Override
    public void setState(final boolean isOn) {
        if (this.isOn != isOn) {
            this.isOn = isOn;
            if (isOn) {
                super.toggleSvgPreset(onPreset);
            } else {
                super.toggleSvgPreset(offPreset);
            }
        }
    }
@param onPreset  The face to display when in the ON state, e.g. an OFF icon
@param offPreset The face to display when in the OFF state, e.g. an ON icon
stroom-core-client-widget/src/main/java/stroom/widget/button/client/SvgToggleButton.java