chromium/chrome/test/data/background_sync/background_sync_browsertest.html

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>BackgroundSyncBrowserTest helper page</title>
    <script src="../format_error.js"></script>
    <script src="background_sync_browsertest.js"></script>
  </head>
  <body>
    <!-- Logic located in background_sync_browsertest.js. -->
  </body>
</html>