Bug 135284 [Viewers] API: need to add methods to StructuredViewer to support ViewerComparator
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
*/
	protected abstract void doUpdateItem(Widget item, Object element, boolean fullMap);
	/**
	 * Compares two elements for equality. Uses the element comparer if one has
	 * been set, otherwise uses the default <code>equals</code> method on the
	 * elements themselves.
	 * 
	 * @param elementA
	 *            the first element
	 * @param elementB
	 *            the second element
	 * @return whether elementA is equal to elementB
	 */
	protected boolean equals(Object elementA, Object elementB) {
		if (comparer == null) {
			return elementA == null ? elementB == null : elementA.equals(elementB);
		} else {
			return elementA == null ? elementB == null : comparer.equals(elementA, elementB);
		}
	}
	/**
	 * Returns the result of running the given elements through the filters.
	 * 
	 * @param elements
	 *            the elements to filter
	 * @return only the elements which all filters accept
	 */
	protected Object[] filter(Object[] elements) {
		if (filters != null) {
			ArrayList filtered = new ArrayList(elements.length);