I have an upcoming interview with google for an EM position. I selected code review over coding, as I have not coded in a while. What to expect from this interview and how to prepare?

I expect the interviewer is going to present a broken code to review.

What I am not clear on are they looking for me to spot general coding errors? Variable initialization, typos, general testability, and structure of the code a.k.a readability/maintainability, logical errors, efficiency, data structures?

How do they choose the code fragments? google code base or leetcode?