Bug 261506 [CommonNavigator] NavigatorDNDService seems like it can use only interfaces
The NavigatorDNDService class seems like it could use only interface APIs and function properly. Patch attached.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonDropAdapter.java
*/
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.ViewerDropAdapter#getBounds(org.eclipse.swt.widgets.Item)
	 */
	public Rectangle getBounds(Item item) {
		return super.getBounds(item);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.ViewerDropAdapter#getCurrentLocation()
	 */
	public int getCurrentLocation() {
		return super.getCurrentLocation();
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.ViewerDropAdapter#getCurrentOperation()
	 */
	public int getCurrentOperation() {
		return super.getCurrentOperation();
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.ViewerDropAdapter#getCurrentTarget()
	 */