chromium/ash/webui/personalization_app/resources/js/ambient/ambient_duration_element.html

<style include="common md-select">
  .ambient-subpage-element-title {
    margin-bottom: 0;
    margin-inline-start: 0px;
  }

  .md-select {
    margin-block-start: 20px;
    margin-inline-end: 8px;
  }
</style>
<div class="ambient-toggle-row">
  <h3 class="ambient-subpage-element-title" id="ambientDurationTitle">
    $i18n{ambientModeDurationTitle}
  </h3>
  <select id="durationOptions" class="md-select"
      on-change="onOptionChanged_" aria-labelledby="ambientDurationTitle">
    <template is="dom-repeat" items="[[options_]]" as="option">
      <option value="[[option]]"
          selected="[[isEqual_(option, selectedDuration_)]]">
        [[getDurationLabel_(option)]]
      </option>
    </template>
  </select>
</div>