Test ufo animation time graph with firefox not complete flat?

[wiseude]

After uninstalling/installing firefox I've noticed this test is not as smooth as it used to be.The only extension I'm using is ublock origin.
Firefox


Chrome


I even tried to refresh firefox 1 more time but it;s staying like this.It's acting as if hardware acceleration is disabled when it's actually enabled (on firefox)

Or is this normal for firefox?