ash/webui/personalization_app/resources/trusted/personalization_theme_element.html

<style include="common-style">
</style>
<div id="container">
  <h2>[[i18n('themeLabel')]]</h2>
  <cr-button id="lightMode" data-color-mode="LIGHT"
      on-click="onClickColorModeButton_"
      aria-pressed$="[[getLightAriaPressed_(darkModeEnabled_)]]">
    <div class="text">[[i18n('lightColorMode')]]</div>
  </cr-button>
  <cr-button id="darkMode" data-color-mode="DARK"
      on-click="onClickColorModeButton_"
      aria-pressed$="[[getDarkAriaPressed_(darkModeEnabled_)]]">
    <div class="text">[[i18n('darkColorMode')]]</div>
  </cr-button>
</div>