Bug 81070 ElementMapper should not use Integer keys computed from System#identityHashCode
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/WorkingSetModel.java
public Object[] getAllParents(Object element) {
    	if (element instanceof IWorkingSet && fActiveWorkingSets.contains(element))
    		return new Object[] {this};
    	return fElementMapper.getAllWorkingSets(element).toArray();
    }
    
    public Object[] addWorkingSets(Object[] elements) {
    	List result= null;
    	for (int i= 0; i < elements.length; i++) {
    		Object element= elements[i];
    		List sets= null;
			if (element instanceof IResource) {
    			sets= fElementMapper.getAllWorkingSetsForResource((IResource)element);
    		} else {
    			sets= fElementMapper.getAllWorkingSets(element);
    		}
			if (sets != null && sets.size() > 0) {
				if (result == null)
					result= new ArrayList(Arrays.asList(elements));
				result.addAll(sets);
			}
		}
    	if (result == null)
    		return elements;
    	return result.toArray();
    }
    
    public boolean needsConfiguration() {
    	return !fConfigured && fActiveWorkingSets.size() == 2 &&
			HistoryWorkingSetUpdater.ID.equals(((IWorkingSet)fActiveWorkingSets.get(0)).getId()) &&