chrome/browser/resources/options/alert_overlay.html

<div class="page hidden" id="alertOverlay">
  <h1 id="alertOverlayTitle"></h1>
  <div class="content-area">
    <div id="alertOverlayMessage"></div>
  </div>
  <div class="action-area">
    <div class="button-strip">
      <button type="reset" id="alertOverlayCancel"></button>
      <button type="submit" id="alertOverlayOk"></button>
    </div>
  </div>
</div>