Bug 158065 [DataBinding] ValidationError observables need a nudge to hook themselves up
See attached patch.
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/observable/value/ComputedValue.java
/*******************************************************************************
 * Copyright (c) 2005, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.databinding.observable.value;
import org.eclipse.jface.databinding.observable.IChangeListener;
import org.eclipse.jface.databinding.observable.IObservable;
import org.eclipse.jface.databinding.observable.IStaleListener;
import org.eclipse.jface.databinding.observable.ObservableTracker;
/**
 * A Lazily calculated value that automatically computes and registers listeners
 * on its dependencies as long as all of its dependencies are IObservable
 * objects
 * 
 * @since 1.0
 */
public abstract class ComputedValue extends AbstractObservableValue {