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
if (showProjects()) 
			return new PackageExplorerLabelProvider(AppearanceAwareLabelProvider.DEFAULT_TEXTFLAGS | JavaElementLabels.P_COMPRESSED,
				AppearanceAwareLabelProvider.DEFAULT_IMAGEFLAGS | JavaElementImageProvider.SMALL_ICONS,
				fContentProvider);
		else
			return new WorkingSetAwareLabelProvider(AppearanceAwareLabelProvider.DEFAULT_TEXTFLAGS | JavaElementLabels.P_COMPRESSED,
				AppearanceAwareLabelProvider.DEFAULT_IMAGEFLAGS | JavaElementImageProvider.SMALL_ICONS,
				fContentProvider);			
	}
	
	private IElementComparer createElementComparer() {
		if (showProjects()) 
			return null;
		else
			return WorkingSetModel.COMPARER;
	}
	
	private void fillActionBars() {
		IActionBars actionBars= getViewSite().getActionBars();
		fActionSet.fillActionBars(actionBars);
	}
	
	private Object findInputElement() {
		if (showWorkingSets()) {
			return fWorkingSetModel;
		} else {
			Object input= getSite().getPage().getInput();
			if (input instanceof IWorkspace) { 
				return JavaCore.create(((IWorkspace)input).getRoot());
			} else if (input instanceof IContainer) {