Bug 81421 Closing a project with open editors leaves stale elements in Package Explorer's working set layout
I20041216-0800 Closing a project with open editors leaves stale elements in Package Explorer's working sets mode. This only affects CUs not normal resources.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/HistoryWorkingSetUpdater.java
private Tracker fTracker;
	private IElementChangedListener fJavaListener;
	private int fMaxElements= 15;
	
	public HistoryWorkingSetUpdater() {
		fOpenFiles= new HashSet();
		initListeners();
	}
	
	/**
	 * {@inheritDoc}
	 */
	public void add(IWorkingSet workingSet) {
		Assert.isTrue(fWorkingSet == null);
		fWorkingSet= workingSet;
	}
	
	/**
	 * {@inheritDoc}
	 */
	public boolean remove(IWorkingSet workingSet) {
		Assert.isTrue(fWorkingSet == workingSet);
		fWorkingSet= null;
		return true;
	}
	
	/**
	 * {@inheritDoc}
	 */
	public boolean contains(IWorkingSet workingSet) {