Bug 135284 [Viewers] API: need to add methods to StructuredViewer to support ViewerComparator
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* @return the corresponding widget, or <code>null</code> if none
	 */
	protected final Widget findItem(Object element) {
		Widget[] result = findItems(element);
		return result.length == 0 ? null : result[0];
	}
	/**
	 * Finds the widgets which represent the given element. The returned array
	 * must not be changed by clients; it might change upon calling other
	 * methods on this viewer.
	 * <p>
	 * The default implementation of this method tries first to find the widget
	 * for the given element assuming that it is the viewer's input; this is
	 * done by calling <code>doFindInputItem</code>. If it is not found
	 * there, the widgets are looked up in the internal element map provided that this
	 * feature has been enabled. If the element map is disabled, the widget is
	 * found via <code>doFindInputItem</code>.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 * @return the corresponding widgets
	 * 
	 * @since 3.2
	 */
	protected final Widget[] findItems(Object element) {
		Widget result = doFindInputItem(element);
		if (result != null) {
			return new Widget[] { result };
		}