chrome/browser/resources/options/language_add_language_overlay.html

<div id="add-language-overlay-page" class="page" role="dialog" hidden>
  <div class="close-button"></div>
  <h1 i18n-content="addLanguageTitle"></h1>
  <div class="content-area">
    <label for="add-language-overlay-language-list"
        i18n-content="addLanguageSelectLabel"></label>
    <select id="add-language-overlay-language-list"></select>
  </div>
  <div class="action-area button-strip">
    <button id="add-language-overlay-cancel-button" i18n-content="cancel">
    </button>
    <button id="add-language-overlay-ok-button" class="default-button"
        i18n-content="ok">
    </button>
  </div>
</div>