Bug 266699 [CommonNavigator] Remove CommonDropAdapter.setCurrentOperation
This has been replaced by overrideOperation() which does the same thing. Note that setCurrentOperation() was added in M5 so it's never really been API yet.
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/extension/TestCopyDropAssistant.java
public IStatus handleDrop(CommonDropAdapter aDropAdapter,
			DropTargetEvent aDropTargetEvent, Object aTarget) {
		return super.handleDrop(aDropAdapter, aDropTargetEvent, aTarget);
	}
	public IStatus validateDrop(Object target, int operation,
			TransferData transferType) {
		
		DropTargetEvent event = getCurrentEvent();
		Assert.isTrue(event != null);
		
		
		getCommonDropAdapter().setCurrentOperation(DND.DROP_COPY);
		return super.validateDrop(target, operation, transferType);
	}
}