Bug 305703 [Viewers][CommonNavigator] remembered contributions can leak when using filters
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
boolean expanded = expandedElements.remove(data) != null;
				if (expanded != getExpanded(item)) {
					if (expanded) {
						createChildren(item);
					}
					setExpanded(item, expanded);
				}
			}
			if (expandedElements.size() > 0) {
				internalSetExpanded(expandedElements, item);
			}
		}
	}
	/**
	 * Sets the expanded state of all items to correspond to the given set of
	 * expanded tree paths.
	 *
	 * @param expandedTreePaths
	 *            the set (element type: <code>TreePath</code>) of elements
	 *            which are expanded
	 * @param widget
	 *            the widget
	 */
	private void internalSetExpandedTreePaths(
			CustomHashtable expandedTreePaths, Widget widget,
			TreePath currentPath) {
		Item[] items = getChildren(widget);
		for (int i = 0; i < items.length; i++) {