<html>
<script language=javascript>

function draw() {
  var canv = document.getElementById("canv");
  var ctx = canv.getContext("2d");
  try {
    canv.width = 50000;
  } catch (e) { }

  ctx.clearRect(0, 0, 10, 10);
}

</script>
<body onload="draw()">
<canvas id="canv" width="5" height="5"></canvas>
</body>
</html>