Defines a viewport tag generator class that will be used for generating the
 * content of a viewport tag that will be added to the HTML of the host page of
 * a UI class.
 * <p>
 * If you want to use the same viewport values for all requests, you can use the
 * simpler {@link Viewport} annotation instead.
Defines a viewport tag generator class that will be used for generating the
 * content of a viewport tag that will be added to the HTML of the host page of
 * a UI class.
 * <p>
 * If you want to use the same viewport values for all requests, you can use the
 * simpler {@link Viewport} annotation instead. | ViewportGeneratorClass.java