people forget lesson from recent past. i don't know when google strong armed w3c to include this back... but we had this since ie4 days and then disabled everywhere since it was abused left and right for click jacking attacks.

Not until Mozilla stops telling websites that I want a light color scheme if I turn it on. privacy.resistFingerprinting does too many things and you shouldn't need to use that sledgehammer to prevent the browser from leaking information that no website should know.