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
static final String TAG_CURRENT_FRAME= "currentFramge"; 
	static final String TAG_ROOT_MODE= "rootMode"; 
	
	private int fRootMode;
	private WorkingSetModel fWorkingSetModel;
	
	private PackageExplorerLabelProvider fLabelProvider;	
	private PackageExplorerContentProvider fContentProvider;
	private FilterUpdater fFilterUpdater;
	
	private PackageExplorerActionGroup fActionSet;
	private ProblemTreeViewer fViewer; 
	private Menu fContextMenu;		
	
	private IMemento fMemento;	
	private ISelectionChangedListener fSelectionListener;
	
	private String fWorkingSetName;
	
	private IPartListener fPartListener= new IPartListener() {
		public void partActivated(IWorkbenchPart part) {
			if (part instanceof IEditorPart)
				editorActivated((IEditorPart) part);
		}
		public void partBroughtToTop(IWorkbenchPart part) {
		}
		public void partClosed(IWorkbenchPart part) {
		}
		public void partDeactivated(IWorkbenchPart part) {
		}