They were on Perforce for a long time. See e.g. https://info.perforce.com/rs/perforce/images/GoogleWhitePaper-StillAllonOneServer-PerforceatScale.pdf https://i

They were on Perforce for a long time. See e.g. https://info.perforce.com/rs/perforce/images/GoogleWhitePaper-StillAllonOneServer-PerforceatScale.pdf https://info.perforce.com/rs/perforce/images/GoogleWhitePape... and https://news.ycombinator.com/item?id=15889958 https://news.ycombinator.com/item?id=15889958.