Bug 147530 [DataBinding] Provide event objects for change listeners
Before data binding goes 1.0 it would be wise to provide EventObjects for the following listeners to ensure that the API doesn't preclude future expansion of the values supplied to listeners. Interfaces that would be affected: * IValueChangeListener * IValueChangingListener * IListChangeListener * ISetChangeListener * IMappingChangeListener
bundles/org.eclipse.core.databinding/src/org/eclipse/core/databinding/observable/set/UnionSet.java
/**
	 * child sets
	 */
	private IObservableSet[] childSets;
	private boolean stale = false;
	/**
	 * Map of elements onto Integer reference counts. This map is constructed
	 * when the first listener is added to the union set. Null if nobody is
	 * listening to the UnionSet.
	 */
	private HashMap refCounts = null;
	private StalenessTracker stalenessTracker;
	/**
	 * @param childSets
	 */
	public UnionSet(IObservableSet[] childSets) {
		super(childSets[0].getRealm(), null, childSets[0].getElementType());
		this.childSets = childSets;
		this.stalenessTracker = new StalenessTracker(childSets,
				stalenessConsumer);
	}