Is border-image-source supported?
HTML
<div id="linear-gradient">fgdgdf</div>
CSS
#linear-gradient {
border-width: 1px;
background-image: -webkit-gradient(radial, right top, 10, 90% 0%, 150, from(#000), to(transparent));
background-image: -webkit-radial-gradient(right top, 150px 230px, #000, transparent);
background-image: -moz-radial-gradient(right top, farthest-corner, #000 0%, transparent 72%);
}