Bug 219909 [DataBinding] UnmodifiableObservableValue
UnmodifiableObservableValue with test cases
bundles/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/Observables.java
* @since 1.1
	 */
	public static IObservableValue constantObservableValue(Object value) {
		return constantObservableValue(Realm.getDefault(), value, null);
	}
	/**
	 * Returns an unmodifiable observable list backed by the given observable
	 * list.
	 * 
	 * @param list
	 *            the list to wrap in an unmodifiable list
	 * @return an unmodifiable observable list backed by the given observable
	 *         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
	 */