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
fResourceToItemsMapper.removeFromMap(element, (Item) item);
			}
			if (l.size() == 0)
				fAdditionalMappings.remove(element);
		}
		protected void unmapAllElements() {
			fAdditionalMappings.clear();
			super.unmapAllElements();
		}
		public void remove(Object[] elements) {
			super.remove(elements);
			List stillExisting= new ArrayList();
			do {
				stillExisting.clear();
				for (int i= 0; i < elements.length; i++) {
					if (findItem(elements[i]) != null)
						stillExisting.add(elements[i]);
				}
				if (stillExisting.size() > 0)
					super.remove(stillExisting.toArray());
			} while (stillExisting.size() > 0);
		}
		protected void internalRefresh(Object element, boolean updateLabels) {
			List l= (List)fAdditionalMappings.get(element);
			if (l == null) {
				super.internalRefresh(element, updateLabels);
			} else {
				List stable= new ArrayList(l);
				super.internalRefresh(element, updateLabels);
				for (Iterator iter= stable.iterator(); iter.hasNext();) {