Bug 263845 [CommonNavigator] Drag/drop folder from non-Java Proj to Java Proj does copy instead of move sometimes
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonDropAdapter.java
* extensions provided by the associated {@link INavigatorContentService}.
 * 
 * <p>
 * Clients should not need to create an instance of this class unless they are
 * creating their own custom viewer. Otherwise, {@link CommonViewer} configures
 * its drop adapter automatically.
 * </p>
 *  
 * 
 * @see INavigatorDnDService
 * @see CommonDragAdapter
 * @see CommonDragAdapterAssistant
 * @see CommonDropAdapterAssistant
 * @see CommonViewer
 * @since 3.2
 */
public final class CommonDropAdapter extends PluginDropAdapter {
	private static final Transfer[] SUPPORTED_DROP_TRANSFERS = new Transfer[] {
			LocalSelectionTransfer.getTransfer(), FileTransfer.getInstance(),
			PluginTransfer.getInstance() };
	private final INavigatorContentService contentService;
	private final INavigatorDnDService dndService;
	
	/**
	 * Create a DropAdapter that handles a drop based on the given content
	 * service and selection provider.
	 * 
	 * @param aContentService
	 *            The content service this Drop Adapter is associated with
	 * @param aStructuredViewer