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chromium/third_party/blink/web_tests/fast/events/touch/resources/frame-touchevent-forwarder.html 

<!DOCTYPE html>
<style>
html {
  border: 1px solid blue;
  box-sizing: border-box;
  width: 100%;
  height: 100%;
}
</style>
<script>
    document.addEventListener('touchstart', function(e) {
        parent.onTouchStart(e);
    });
</script>
Iframe