final HandlerRegistration addValueChangeHandler(ValueChangeHandler<List<T>> handler) {
        return addHandler(handler, ValueChangeEvent.getType());
    }
Add a {@link ValueChangeHandler} that is called when the display values
change. Used by {@link CellBrowser} to detect when the displayed data
changes.

@param handler the handler
@return a {@link HandlerRegistration} to remove the handler
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/AbstractHasData.java