Bug 137849 Unable to set comparator in StructuredViewer
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* If <code>fullMap</code> is <code>true</code> then the current mapping
	 * from element to widgets is removed and the new mapping is added. If
	 * fullmap is <code>false</code> then only the new map gets installed.
	 * Installing only the new map is necessary in cases where only the order of
	 * elements changes but not the set of elements.
	 * <p>
	 * This method is internal to the framework; subclassers should not call
	 * this method.
	 * </p>
	 * 
	 * @param item
	 * @param element element
	 * @param fullMap
	 *            <code>true</code> if mappings are added and removed, and
	 *            <code>false</code> if only the new map gets installed
	 */
	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) {