Bug 127105 Package explorer hierarchical mode calls ICompilationUnit#getChildren() in PackageExplorerProblemTreeViewer#isExpandable
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"; 
	static final String SETTING_MEMENTO= "memento"; 
	
	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 ISelection fLastOpenSelection;
	private ISelectionChangedListener fPostSelectionListener;
	
	private String fWorkingSetLabel;
	
	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) {