@Override
    public void setEnabled(final boolean enabled) {
        super.setEnabled(enabled);
        if (enabled) {
            getElement().removeClassName("disabled");
        } else {
            getElement().addClassName("disabled");
        }
    }
Used to decide whether to allow clicks to propagate up to the superclass
or container elements.
stroom-core-client-widget/src/main/java/stroom/widget/button/client/BaseSvgButton.java