third_party/WebKit/LayoutTests/virtual/threaded/fast/idleToBlob/OffscreenCanvas-convertToBlob-webgl-worker-expected.html

<img id="png"/>
<script>
if (window.testRunner) {
  testRunner.waitUntilDone();
}

var pngImage = document.getElementById('png');
function imageLoaded() {
  if (window.testRunner) {
    window.testRunner.notifyDone();
  }
}
pngImage.addEventListener('load', imageLoaded);

var canvas = document.createElement("canvas");
canvas.width = 50;
canvas.height = 50;
var gl = canvas.getContext('webgl');
gl.clearColor(0, 1, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT);

canvas.toBlob(function(blob) {
  pngImage.src = URL.createObjectURL(blob);
});
</script>