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

<state-banner>
  <span slot="text">$i18n{UNKNOWN_FILESYSTEM_WARNING}</span>
  <cr-button slot="extra-button" command="#format">
    $i18n{FORMAT_DEVICE_BUTTON_LABEL}
  </cr-button>
</state-banner>