It was in fact the EdgeTPU (which is different from the TPU used in data centers).
The talk from a google engineer can be found on youtube: https://www.youtube.com/watch?v=x85342Cny8c
Please note that they were using a version of Chisel from 5+ years ago and many things have changed since then.
It is still true though that Chisel can be hard to learn for typical hardware engineers, which is why it may be best suited for small and highly dedicated teams rather then large hardware companies.
The talk from a google engineer can be found on youtube: https://www.youtube.com/watch?v=x85342Cny8c Please note that they were using a version of Chisel from 5+ years ago and many things have changed since then. It is still true though that Chisel can be hard to learn for typical hardware engineers, which is why it may be best suited for small and highly dedicated teams rather then large hardware companies.
[EDIT] Here is a talk from a solo-developer using the latest version of Chisel: https://www.youtube.com/watch?v=Wst8IoYRWKo