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chromium/third_party/blink/renderer/core/testing/data/ime-on-focus-on-user-gesture.html 

<!DOCTYPE html>
<div id="button" style="width: 200px; height: 200px"></div>
<input type="text" id="input"></input>
<script>
document.querySelector("#button").addEventListener("click", function() {
    document.querySelector("#input").focus();
});
</script>