The page you linked to says: > GL layers acceleration is not yet enabled by default (see bug 594876). You can enable it by setting layers.acceleration.force-en

The page you linked to says: > GL layers acceleration is not yet enabled by default (see bug 594876). You can enable it by setting layers.acceleration.force-enabled=true in about:config. That means off by default. Also maybe relevant is that I'm on the Firefox Graphics team so I have some knowledge of this. If you want to verify, download a stock Firefox build from Mozilla, run it on a new profile, and check what it says for Compositing in the Graphics section. OpenGL means acceleration, Basic means software.