private void ensureSpinner() {
        if (spinner == null) {
            synchronized (ValueSpinnerCell.class) {
                if (spinner == null) {
                    spinner = new Spinner();
                }
            }
        }
    }
The currently focused value key. Only one key can be focused at any time.
stroom-core-client-widget/src/main/java/stroom/cell/valuespinner/client/ValueSpinnerCell.java