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
import org.eclipse.ui.part.IShowInSource;
import org.eclipse.ui.part.IShowInTarget;
import org.eclipse.ui.part.IShowInTargetList;
import org.eclipse.ui.part.ResourceTransfer;
import org.eclipse.ui.part.ShowInContext;
import org.eclipse.ui.part.ViewPart;
import org.eclipse.ui.views.framelist.FrameAction;
import org.eclipse.ui.views.framelist.FrameList;
import org.eclipse.ui.views.framelist.IFrameSource;
import org.eclipse.ui.views.framelist.TreeFrame;
import org.eclipse.ui.views.navigator.LocalSelectionTransfer;
import org.eclipse.jdt.core.IClassFile;
import org.eclipse.jdt.core.ICompilationUnit;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.core.IJavaModel;
import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.jdt.core.IPackageFragment;
import org.eclipse.jdt.core.IType;
import org.eclipse.jdt.core.JavaCore;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.internal.corext.util.JavaModelUtil;
import org.eclipse.jdt.ui.IPackagesViewPart;
import org.eclipse.jdt.ui.JavaElementLabels;
import org.eclipse.jdt.ui.JavaElementSorter;
import org.eclipse.jdt.ui.JavaUI;
import org.eclipse.jdt.ui.PreferenceConstants;
import org.eclipse.jdt.ui.StandardJavaElementContentProvider;
import org.eclipse.jdt.ui.actions.CustomFiltersActionGroup;
import org.eclipse.jdt.internal.ui.IJavaHelpContextIds;
import org.eclipse.jdt.internal.ui.JavaPlugin;