Just marvel at how much data/metadata they get from that little trick when multiplied by millions users.
This is the most fantastic way to target and exploit any single Android user anywhere in the world that I've ever heard of. Automatic, hard to avoid, easy to implement, and the user has no idea.
At first, I thought this can't be true because, surely, Google marks its cookies as HTTPS-only, right? So I checked, and turns out about half the cookies google.com has in my browser are not HTTPS-only. In fact, the HTTPS-only cookies it does have seem to be the same set of cookies, just with a '__Secure-' prefix. Similarly, about half (different set) of the cookies JS accessible.