$ ./mach run --device-pixel-ratio=1 tests/html/get-natural-height.html
    ALERT: width: 600, height: 254
    $ ./mach run --device-pixel-ratio=2 tests/html/get-natural-height.html
    ALERT: width: 600, height: 254
    $ ./mach run --device-pixel-ratio=.5 tests/html/get-natural-height.html
    ALERT: width: 600, height: 254

It doesn't. Answers #6769.