Bug 81877 Package explorer forgets active working set [package explorer]
3.1 M4 1. open pkg explorer. 2. select a working set, pkg explorer updates and filters out projects. 3. close pkg explorer. 4. open package explorer again and the working set is no longer applied. This used to work.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
/**
		 * {@inheritDoc}
		 */
		protected Object[] addAditionalProblemParents(Object[] elements) {
			if (showWorkingSets()) {
				return fWorkingSetModel.addWorkingSets(elements);
			}
			return elements;
		}
		
		
		
		protected Object[] getSortedChildren(Object parent) {
			IParentAwareSorter sorter= getSorter() instanceof IParentAwareSorter 
				? (IParentAwareSorter)getSorter()
				: null;
			if (sorter != null)
				sorter.setParent(parent);
			try {
				return super.getSortedChildren(parent);
			} finally {
				if (sorter != null)
					sorter.setParent(null);
			}
		}
		
		
		
		Map fAdditionalMappings= new HashMap();
		protected void mapElement(Object element, Widget item) {