So how does this work? Where does Chromium get the data for the websites which load slow? Does this mean that websites which one visits get sent to Google now?

So how does this work? Where does Chromium get the data for the websites which load slow? Does this mean that websites which one visits get sent to Google now? Or do they use the existing SafeBrowsing queries to also send page load times? What are the implications of this for tracking?