bonut

<script>
        $(document).ready(function () {

            var grad = $('.p_border_r').css('background');
            var deg = 45;
            var lastms = 0;
            var animate = true;

            var callback = function (time) {
                if (lastms == 0) {
                    lastms = time;
                }
                deg = (deg + (time - lastms) * 0.3);
                lastms = time;
                while (deg > 360) {
                    deg -= 360;
                }
                var newCss = grad.replace('45deg', deg + 'deg');

                $('.p_border_r').css('background', newCss);
                if (animate) {
                    window.requestAnimationFrame(callback);
                } else {
                    lastms = 0;
                }
            };

            window.requestAnimationFrame(callback);

        })
    </script>