Google is mailing its customers with "Important updates about the General Data Protection Regulation (GDPR)." There are several links in that e-mail, but the link of the interest is "Updated EU User Consent Policy" (https://www.google.com/about/company/consentstaging.html).
In that document, Google is stating:
You must obtain end users’ legally valid consent to:
When seeking consent you must:
If you're using some of the Google services (not just Google Analytics), as we do, I suggest taking a look.