Rated 5 out of 5 stars

Από τον/την Vojtano στις Αύγ. 2, 2016 · μόνιμος σύνδεσμος

Don't trust that other comment. It works this way, but you must have an AMOLED screen. I do have it and this is exactly what makes my firefox more efficient.
It's a must for all AMOLED screen users ;-)