Bug 16308 [DND] dnd from os to navigator shows an incorrect icon
smoke test for 0518 it shows a move icon although move will not happen
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/navigator/NavigatorDropAdapter.java
private int lastValidOperation = DND.DROP_NONE;
	/**
	 * Constructs a new drop adapter.
	 */
	public NavigatorDropAdapter(StructuredViewer viewer) {
		super(viewer);
	}
	/**
	 * @see org.eclipse.swt.dnd.DropTargetListener#dragEnter(DropTargetEvent)
	 */
	public void dragEnter(DropTargetEvent event) {
		if (event.getSource() == event.widget) {
			IStructuredSelection selection = (IStructuredSelection) getViewer().getSelection();
			List sourceList = selection.toList();
			sourceResources = (IResource[]) sourceList.toArray(new IResource[sourceList.size()]);
		}
		else {
			sourceResources = null;
		}
		super.dragEnter(event);
	}
	/**
	 * @see org.eclipse.swt.dnd.DropTargetListener#dragLeave(DropTargetEvent)
	 */
	public void dragLeave(DropTargetEvent event) {
		sourceResources = null;
		super.dragLeave(event);
	}
	/**
	 * @see DropTargetListener#dragOver