when you're viewing an image, chrome helpfully options two versions: fit-to-screen or 1:1 zoom. you can kind of adjust this with actual in-browser zooming as well, which isn't tied into this because ?????????? (car tires squeak, sound of trash cans exploding, random cat meows)
but beyond that: fit width/height. you know, like "fit to width" when you're viewing a pdf or whatever.
there is almost surely an extension that does this somewhere, it's just a surprising lack when you realize how useful it would end up being.
