Bug 27764 IResource.findMarkers is called too often
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
import org.eclipse.jdt.ui.IPackagesViewPart;
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.internal.ui.IJavaHelpContextIds;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.dnd.DelegatingDragAdapter;
import org.eclipse.jdt.internal.ui.dnd.DelegatingDropAdapter;
import org.eclipse.jdt.internal.ui.dnd.LocalSelectionTransfer;
import org.eclipse.jdt.internal.ui.dnd.ResourceTransferDragAdapter;
import org.eclipse.jdt.internal.ui.dnd.TransferDragSourceListener;
import org.eclipse.jdt.internal.ui.dnd.TransferDropTargetListener;
import org.eclipse.jdt.internal.ui.javaeditor.EditorUtility;
import org.eclipse.jdt.internal.ui.javaeditor.IClassFileEditorInput;
import org.eclipse.jdt.internal.ui.javaeditor.JarEntryEditorInput;
import org.eclipse.jdt.internal.ui.util.JavaUIHelp;
import org.eclipse.jdt.internal.ui.viewsupport.AppearanceAwareLabelProvider;
import org.eclipse.jdt.internal.ui.viewsupport.IViewPartInputProvider;
import org.eclipse.jdt.internal.ui.viewsupport.JavaElementImageProvider;
import org.eclipse.jdt.internal.ui.viewsupport.JavaElementLabels;
import org.eclipse.jdt.internal.ui.viewsupport.ProblemTreeViewer;
import org.eclipse.jdt.internal.ui.viewsupport.StatusBarUpdater;
/**
 * The ViewPart for the ProjectExplorer. It listens to part activation events.
 * When selection linking with the editor is enabled the view selection tracks
 * the active editor page. Similarly when a resource is selected in the packages
 * view the corresponding editor is activated. 
 */
public class PackageExplorerPart extends ViewPart implements ISetSelectionTarget, IMenuListener, IPackagesViewPart,  IPropertyChangeListener, IViewPartInputProvider {