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#validateDrop(java.lang.Object,
	 *      int, org.eclipse.swt.dnd.TransferData)
	 */
	public boolean validateDrop(Object aDropTarget, int theDropOperation,
			TransferData theTransferData) {
		if (Policy.DEBUG_DND) {
			System.out.println("CommonDropAdapter.validateDrop (begin)"); 
		}
		boolean result = false;
		IStatus valid = null;
		if (super.validateDrop(aDropTarget, theDropOperation, theTransferData)) {
			result = true; 
		} else {
			Object target = aDropTarget != null ? aDropTarget : getViewer().getInput();
			CommonDropAdapterAssistant[] assistants = dndService
					.findCommonDropAdapterAssistants(target,
							theTransferData);
			if (Policy.DEBUG_DND) {
				System.out
						.println("CommonDropAdapter.validateDrop found " + assistants.length + " drop assistants"); 
				for(int i=0; i<assistants.length; i++)
					System.out.println("CommonDropAdapter.validateDrop :" + assistants[i].getClass().getName()); 
				
			}
			for (int i = 0; i < assistants.length; i++) {