Bug 305703 [Viewers][CommonNavigator] remembered contributions can leak when using filters
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
Item previous = getPreviousItem(current);
			showItem(previous == null ? current : previous);
			return previous;
		}
		return null;
	}
	/**
	 * Sets the auto-expand level to be used when the input of the viewer is set
	 * using {@link #setInput(Object)}. The value 0 means that there is no
	 * auto-expand; 1 means that the invisible root element is expanded (since
	 * most concrete subclasses do not show the root element, there is usually
	 * no practical difference between using the values 0 and 1); 2 means that
	 * top-level elements are expanded, but not their children; 3 means that
	 * top-level elements are expanded, and their children, but not
	 * grandchildren; and so on.
	 * <p>
	 * The value <code>ALL_LEVELS</code> means that all subtrees should be
	 * expanded.
	 * </p>
	 * <p>
	 * Note that in previous releases, the Javadoc for this method had an off-by
	 * one error. See bug 177669 for details.
	 * </p>
	 * 
	 * @param level
	 *            non-negative level, or <code>ALL_LEVELS</code> to expand all
	 *            levels of the tree
	 */
	public void setAutoExpandLevel(int level) {
		expandToLevel = level;