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
protected Widget internalGetWidgetToSelect(Object element) {
			Widget result= findItem(element);
			if (!(result instanceof TreeItem))
				return result;
			if (isInHistroyWorkingSet((TreeItem)result)) {
				List l= (List)fAdditionalMappings.get(element);
				if (l != null && !l.isEmpty()) {
					return (Widget)l.get(0);
				} else {
					
					
					return null;
				}
			}
			return result;
		}
		private boolean isInHistroyWorkingSet(TreeItem item) {
			TreeItem parent= item.getParentItem();
			while (parent != null) {
				Object data= getElement(parent);
				if (data instanceof IWorkingSet && HistoryWorkingSetUpdater.ID.equals(((IWorkingSet)data).getId()))
					return true;
				parent= parent.getParentItem();
			}
			return false;
		}
	    protected boolean isSameSelection(List items, Item[] current) {
	    	if (items.size() != current.length)
	    		return false;
	    	Set newSelection= new HashSet(items);