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chromium/third_party/blink/web_tests/external/wpt/fetch/metadata/resources/appcache-iframe.sub.html 

<!DOCTYPE html>
<html lang="en" manifest="{{GET[manifest]}}">
<script>
if (!window.applicationCache) {
  parent.postMessage('application cache not supported');
} else {
  applicationCache.onnoupdate =
    applicationCache.ondownloading =
    applicationCache.onobsolete =
    applicationCache.onerror = function() {
      parent.postMessage('okay');
    };
}
</script>
</html>