Bug 219909 [DataBinding] UnmodifiableObservableValue
UnmodifiableObservableValue with test cases
bundles/org.eclipse.core.databinding/src/org/eclipse/core/databinding/observable/Observables.java
*            the observable's realm
	 * @param value
	 *            the observable's constant value
	 * @return an immutable observable value with the given constant value
	 * @since 1.1
	 */
	public static IObservableValue constantObservableValue(Realm realm,
			Object value) {
		return constantObservableValue(realm, value, null);
	}
	/**
	 * Returns an observable value with the given constant value.
	 * 
	 * @param value
	 *            the observable's constant value
	 * @param valueType
	 *            the observable's value type
	 * @return an immutable observable value with the given constant value
	 * @since 1.1
	 */
	public static IObservableValue constantObservableValue(Object value,
			Object valueType) {
		return constantObservableValue(Realm.getDefault(), value, valueType);
	}
	/**
	 * Returns an observable value with the given constant value.
	 * 
	 * @param value
	 *            the observable's constant value
	 * @return an immutable observable value with the given constant value