chromium/chrome/browser/resources/settings/site_settings/pdf_documents.html

    <style include="settings-shared">
    .secondary {
      margin-top: 0;  /* Cancel separation between main and secondary text. */
    }
    </style>
    <settings-toggle-button id="toggle" class="two-line"
        label="$i18n{siteSettingsPdfDownloadPdfs}"
        pref="{{prefs.plugins.always_open_pdf_externally}}">
    </settings-toggle-button>