Bug 127861 [DataBinding] Mark API provisional
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/updatables/UnionSet.java
if (refCount == null) {
				adds.add(next);
				refCount = new Integer(1);
				refCounts.put(next, refCount);
			} else {
				refCount = new Integer(refCount.intValue() + 1);
				refCounts.put(next, refCount);
			}
		}
		return adds;
	}
	protected Collection computeElements() {
		
		if (refCounts == null) {
			HashSet result = new HashSet();
			
			for (Iterator iter = childSets.iterator(); iter.hasNext();) {
				IReadableSet next = (IReadableSet) iter.next();
				
				result.addAll(next.toCollection());
			}
			
			return result;
		}
		
		
		return refCounts.keySet();
	}
}