Bug 81426 Package Explorer shows nothing after drill into working set, then show projects
I200412160800 - switch Package Explorer to working sets - context menu > Go Into a working set - Show > Projects -> view is empty -> view toolbar button 'Up to Working Sets' does not do anything
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
MultiElementSelection toRestore= (MultiElementSelection)selection;
			List pathsToSelect= new ArrayList();
			for (Iterator iter= toRestore.iterator(); iter.hasNext();) {
				Object element= iter.next();
				TreePath[] pathsToRestore= toRestore.getTreePaths(element);
				CustomHashtable currentParents= createRootAccessedMap(contentProvider.getTreePaths(element));
				for (int i= 0; i < pathsToRestore.length; i++) {
					TreePath path= pathsToRestore[i];
					Object root= path.getFirstSegment();
					if (root != null && path.equals((TreePath)currentParents.get(root), getComparer())) {
						pathsToSelect.add(path);
					}
				}
			}
			List toSelect= new ArrayList();
			for (Iterator iter= pathsToSelect.iterator(); iter.hasNext();) {
				TreePath path= (TreePath)iter.next();
				int size= path.getSegmentCount();
				if (size == 0)
					continue;
				Widget current= getTree();
				int last= size - 1;
				Object segment;
				for (int i= 0; i < size && current != null && (segment= path.getSegment(i)) != null; i++) {
					internalExpandToLevel(current, 1);
					current= internalFindChild(current, segment);
					if (i == last && current != null)
						toSelect.add(current);
				}
			}