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<div>
    <svg xmlns="http://www.w3.org/2000/svg"
          width="526" height="233">
      <rect x="13" y="14" width="500" height="200" rx="50" ry="100"
          fill="none" stroke="blue" stroke-width="10" />
    </svg>
</div>
<canvas></canvas>

var html = document.querySelector("svg").parentNode.innerHTML;
var imgsrc = 'data:image/svg+xml;base64,'+ btoa(html);
var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d");
    canvas.setAttribute('width', 526);
    canvas.setAttribute('height', 233);

var image = new Image;
  image.src = imgsrc;
  image.onload = function() {
      context.drawImage(image, 0, 0);      
      var canvasdata = canvas.toDataURL("image/png");
      var a = document.createElement("a");
      a.textContent = "save";
      a.download = "export_"+Date.now()+".png";
      a.href = canvasdata; 
      document.body.appendChild(a);
      canvas.parentNode.removeChild(canvas);
};

http://jsfiddle.net/a9ude9p0/6/