<html>
<body>
  <script>
function createBlob(blocksize) {
  var blob = new Blob();
  while (blob.size < 25 * 1024 * 1024) { // 25 MB
    blob = new Blob([blob, new Uint8Array(blocksize)]);
  }
  URL.createObjectURL(blob);
}
createBlob(1024 * 25);
  </script>
</body>
</html>
