Bug 218884 [DataBinding] Add API: WorkbenchObservables
... for things like listening to ISelectionService
bundles/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/Observables.java
*         list
	 */
	public static IObservableList unmodifiableObservableList(
			IObservableList list) {
		if (list == null) {
			throw new IllegalArgumentException("List parameter cannot be null."); 
		}
		return new UnmodifiableObservableList(list);
	}
	/**
	 * Returns an unmodifiable observable set backed by the given observable
	 * set.
	 * 
	 * @param set
	 *            the set to wrap in an unmodifiable set
	 * @return an unmodifiable observable set backed by the given observable set
	 * @since 1.1
	 */
	public static IObservableSet unmodifiableObservableSet(IObservableSet set) {
		if (set == null) {
			throw new IllegalArgumentException("Set parameter cannot be null"); 
		}
		return new UnmodifiableObservableSet(set);
	}
	/**
	 * Returns an unmodifiable observable map backed by the given observable
	 * map.
	 * 
	 * @param map
	 *            the map to wrap in an unmodifiable map