As much as I generally like MDv1: I hate those floating buttons with a passion.

They can occasionally work. But the vast majority of the time they simply get in the way and can't be hidden, because you're in a content-edge-case that doesn't scroll far enough, or you simply reached the end and they didn't leave after-end padding to make room for it. And very few actions are so important that you want to display it over everything else, for the same reasons that everyone recommends against popups.

Just put it in the freaking toolbar. Top or bottom, I don't care.