validation-bubble-device-emulation-change.html

<!DOCTYPE html>
<p>Check if a validation bubble is shown at a correct position in correct scale
   with device emulation.</p>
<input pattern="\d{4}" title="Please specify four digits." value="abc"
       style="position:absolute; top: 100px; left: 50px;">
<script src="../../resources/run-after-layout-and-paint.js"></script>
<script>
document.querySelector('input').reportValidity();
if (window.testRunner && window.internals) {
  testRunner.waitUntilDone();
  runAfterLayoutAndPaint(() => {
    internals.setDeviceEmulationScale(0.5);
    runAfterLayoutAndPaint(() => {
      internals.setDeviceEmulationScale(1.25);
      runAfterLayoutAndPaint(() => {
        internals.setDeviceEmulationScale(2);
        runAfterLayoutAndPaint(() => {
          testRunner.notifyDone();
        });
      });
    });
  });
}
</script>

chromium/third_party/blink/web_tests/fast/forms/validation-bubble-device-emulation-change.html