Comment by dlenski

I had the same question (2). https://news.ycombinator.com/item?id=44560664

If it's only in the closed-source Chrome, then it seems it's intended to help Google's servers distinguish between Google's own products and others.

But I've never seen a Google site which worked less-well in Chromium than in Chrome, so I'm somewhat skeptical of this. Perhaps there are exceptions