chromium/ui/file_manager/file_manager/foreground/js/ui/banners/local_disk_low_space_banner.html

<warning-banner>
  <span slot="text">$i18n{DOWNLOADS_DIRECTORY_WARNING}</span>
  <cr-button slot="extra-button" href="$i18n{DOWNLOADS_LOW_SPACE_WARNING_HELP_URL}">
    $i18n{LEARN_MORE_LABEL}
  </cr-button>
  <cr-button slot="dismiss-button" id="dismiss-button">
    $i18n{DRIVE_WELCOME_DISMISS}
  </cr-button>
</warning-banner>