The only thing they really don't open source are web services (Gmail, search) - probably both for competitive reasons but also because it ties in too deeply with their infrastructure.
Chromium and Android being their two largest projects are OS though, and thousands of tools and libraries that they've built. Also TensorFlow, their newest machine learning library.
Most still are. Look at their github. They release an insane amount of OS code.
https://github.com/google/
https://github.com/chromium/
The only thing they really don't open source are web services (Gmail, search) - probably both for competitive reasons but also because it ties in too deeply with their infrastructure.
Chromium and Android being their two largest projects are OS though, and thousands of tools and libraries that they've built. Also TensorFlow, their newest machine learning library.