Bug 156883 [Viewers] enhancements to ILazyTreeContentProvider
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
Widget parentItem = parentItemArray[i];
			if (parentItem instanceof Item) {
				parentItems.put(parentItem, parentItem);
			}
			
			Item[] children = getChildren(parentItem);
			for (int j = 0; j < children.length; j++) {
				Item child = children[j];
				Object data = child.getData();
				if (data != null && toRemove.containsKey(data)) {
					disassociate(child);
					child.dispose();
				}
			}
		}
		internalReconcileParentItems(parentItems);
	}
	/**
	 * Sets the expanded state of all items to correspond to the given set of
	 * expanded elements.
	 * 
	 * @param expandedElements
	 *            the set (element type: <code>Object</code>) of elements
	 *            which are expanded
	 * @param widget
	 *            the widget
	 */
	private void internalSetExpanded(CustomHashtable expandedElements,
			Widget widget) {
		Item[] items = getChildren(widget);