chromium/content/test/data/gpu/pixel_webgl_resized_canvas.html

<!DOCTYPE HTML>
<html>
<head>
<meta name="viewport" content="initial-scale=1">
<title>WebGL Canvas Resize Test</title>
<style type="text/css">
.nomargin {
  margin: 0px auto;
}
</style>
<script>
let g_swapsBeforeAck = 15;

function sendResult(status) {
  if (window.domAutomationController) {
    window.domAutomationController.send(status);
  } else {
    console.log(status);
  }
}

function waitForFinish() {
  if (g_swapsBeforeAck == 0) {
    sendResult("SUCCESS");
  } else {
    g_swapsBeforeAck--;
    window.requestAnimationFrame(waitForFinish);
  }
}

function main() {
  let canvas = document.getElementById("c");
  let gl = canvas.getContext("webgl", {preserveDrawingBuffer: true});
  gl.enable(gl.SCISSOR_TEST);
  gl.scissor(0, 0, 50, 50);
  gl.clearColor(0, 0, 1, 1);
  gl.clear(gl.COLOR_BUFFER_BIT);

  setTimeout(() => {
    canvas.width = 150;
    waitForFinish();
  }, 10);
}
</script>
</head>
<body onload="main()" class="nomargin">
<canvas id="c" width="300" height="300" class="nomargin" style="background-color:red"></canvas>
</body>
</html>