Zoom has some interesting behavior for the CSSOM, since it undoes some of its effects, but only in some APIs.

The original zoom draft by @atanassov makes sense to me:

• You want all getComputedStyle things to be unzoomed, because you want to preserve div.style.foo = getComputedStyle(div).foo round-tripping.
• You might want some of the sizes to be unzoomed.
• But you never want positions to be unzoomed, that makes no sense because the positions are meaningless if you cross a zoom boundary and you unzoom them.

However Blink and WebKit seem to unzoom in things like getBoundingClientRect, ResizeObserver rects, and so on. I don't think those make much sense for the same reason zooming positions doesn't make much sense.

My personal take is that, in general, the less APIs that account for zoom by unzooming, the better.

cc: #5623 @chrishtr @lilles @smfr @tabatkins @atanassov