How to use setOutlineProvider instead of setOutline in Lollipop

Just to complete the @ianhanniballake answer:

Button fab = (Button) findViewById(R.id.fab);
//Outline outline = new Outline();
//outline.setOval(0, 0, size, size);
//fab.setOutline(outline);  
ViewOutlineProvider viewOutlineProvider = new ViewOutlineProvider() {
        @Override
        public void getOutline(View view, Outline outline) {
            // Or read size directly from the view's width/height
            int size = getResources().getDimensionPixelSize(R.dimen.fab_size);
            outline.setOval(0, 0, size, size);
        }
    };
fab.setOutlineProvider(viewOutlineProvider);