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
new FileTransferDragAdapter(fViewer)
		};
		fViewer.addDragSupport(ops, transfers, new JdtViewerDragAdapter(fViewer, dragListeners));
	}
	private void initDrop() {
		int ops= DND.DROP_COPY | DND.DROP_MOVE | DND.DROP_LINK | DND.DROP_DEFAULT;
		Transfer[] transfers= new Transfer[] {
			LocalSelectionTransfer.getInstance(), 
			FileTransfer.getInstance()};
		TransferDropTargetListener[] dropListeners= new TransferDropTargetListener[] {
			new SelectionTransferDropAdapter(fViewer),
			new FileTransferDropAdapter(fViewer),
			new WorkingSetDropAdapter(this)
		};
		fViewer.addDropSupport(ops, transfers, new DelegatingDropAdapter(dropListeners));
	}
	/**
	 * Handles selection changed in viewer.
	 * Updates global actions.
	 * Links to editor (if option enabled)
	 */
	private void handleSelectionChanged(SelectionChangedEvent event) {
		IStructuredSelection selection= (IStructuredSelection) event.getSelection();
		fActionSet.handleSelectionChanged(event);
		if (isLinkingEnabled())
			linkToEditor(selection);
	}
	public void selectReveal(ISelection selection) {
		selectReveal(selection, 0);
	}