It's really not that at level. Once at Google you really get the benefit of doubt of clearing a high bar. It's mostly a talk around your work / perf / CLs and then team fit.
If it's anything like amazon they will just be able to look at all of your code for the last N years which is a very strong signal to go along with interview questions. For internal transfers I general focus more on design questions and check the code history for "can they code IRL". Design is harder to check for and also is more dependent on "can we work together to solve problems" which isn't always apparent from just artifacts.
what is CL?
Change List: internal Google lingo for what is more commonly known as patch, diff, or pull request in the Open source wold.