Bug 153993 [Viewers] Common Baseclass for Tree/TableEditorImpl
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* Returns the SWT child items for the given SWT widget.
	 * 
	 * @param widget
	 *            the widget
	 * @return the child items
	 */
	protected abstract Item[] getChildren(Widget widget);
	/**
	 * Get the child for the widget at index. Note that the default
	 * implementation is not very effecient and should be overridden if this
	 * class is implemented.
	 * 
	 * @param widget
	 *            the widget to check
	 * @param index
	 *            the index of the widget
	 * @return Item or <code>null</code> if widget is not a type that can
	 *         contain items.
	 * 
	 * @throws ArrayIndexOutOfBoundsException
	 *             if the index is not valid.
	 * @since 3.1
	 */
	protected Item getChild(Widget widget, int index) {
		return getChildren(widget)[index];
	}
	/**
	 * Returns whether the given SWT item is expanded or collapsed.
	 * 
	 * @param item