At least, advance notice which might be long depending of the country, probably at least three months in France. Plus, Google will have issues justifying a cut for economic reason in much of Europe. They remain very profitable even if less than before so they might need due cause to fire people.

Generally speaking European laws protect the employees more than the shareholders. You can't really just employ a lot of people when things are doing well expecting to fire them if there is a downturn. It encourages companies to be more conservative regarding hiring which can be both a blessing and a curse.