text: self.addEventListener('fetch', event => {
      if (!event.request.url.match(/body-stream-with-invalid-chunk$/))
        return;
      const stream = new ReadableStream({start: controller => {
          // The argument is intentionally a string, not a Uint8Array.
          controller.enqueue('hello');
        }});
      const headers = { 'x-content-type-options': 'nosniff' };
      event.respondWith(new Response(stream, { headers }));
    });
  