Investigate possible DPI spoofing bypass
OxPoly on twitter claims being able to get the actual DPI of a device while the user is running Tor Browser. The PoC is:
var devicePixelRatio = window.devicePixelRatio || 1;
dpi_x = document.getElementById('testdiv').offsetWidth * devicePixelRatio;
dpi_y = document.getElementById('testdiv').offsetHeight * devicePixelRatio;
alert(dpi_x);
We should verify and if it is indeed an issue fix that.