Neuter fingerprinting with Battery API
Firefox 10 added a battery API that is off by default: https://developer.mozilla.org/en/DOM/window.navigator.mozBattery
Battery properties such as exact capacity, charge rate, and drain rate can provide fingerprinting information.
It looks like the current API does not provide exact capacity, but charge rate and drain rates can be calculated. Probably not a big deal, but it should be trivial to obfuscate/discretize with Object.defineProperty if we need to.