and it's impossible to achieve it without probing those attributes.

some advertising libraries solve that, since the advertising industry deals in in-view ad impressions for a few years now, by being smart about when to do it. the best one is called safeFrames. others like moat detect if the user has a fast computer, abuse it to no end, and then extrapolate the results for the whole audience.

i expect all of them to move to the native APIs soon (but Android fragmentation will make it slow)