chromium/chrome/test/data/android/customtabs/test_window_open.html

<!DOCTYPE html>
<html>
<body>

<p>Click the button to open a new browser window.</p>

<button id="new_window" onclick="myFunction()">Click me</button>

<script>
function myFunction() {
    window.open("about:blank");
}
</script>

</body>
</html>