verify that subpixel accuracy of window scroll properties does not add fingerprinting risk
As of Firefox 55, the window.pageYOffset, pageXOffset, scrollX, and scrollY properties now return data with subpixel accuracy. We think this means "half pixels on a macOS Retina or other high resolution display." We should determine if this adds any fingerprinting risks (and whether the values returned are already rounded when privacy.resistFingerprinting is set to true). See:
https://bugzilla.mozilla.org/show_bug.cgi?id=1151421