Right now you have to create the quiz from the assignment, rather than being able to use a previously existing Google Form, but once the quiz exists, you can edit it from anywhere and treat it like a regular Google Forms quiz.
Students must be using a managed Chromebook (meaning a school-owned device) in order to access the quiz. When they click on the assignment, they will see a message that "locked mode is on" and that when they start the quiz, they will no longer be able to access other tabs. Students can close the quiz but will lose all progress (and you, as the form owner, will be notified). After a student submits the quiz, they will return to "unlocked" mode and resume normal access.
If you try it, send Google your feedback!