Element update tester extension which allows an update policy to selectively
 * flush properties of elements.  This can be useful if the update tester's event
 * only affects a certain aspect of the element's presentation.
Element update tester extension which allows an update policy to selectively
 * flush properties of elements.  This can be useful if the update tester's event
 * only affects a certain aspect of the element's presentation. | IElementUpdateTesterExtension.java