Function concat

packages/react-dom/src/__tests__/ReactDOMFizzStaticBrowser-test.js:74–102

(streamA, streamB)

  }

  function concat(streamA, streamB) {
    const readerA = streamA.getReader();
    const readerB = streamB.getReader();
    return new ReadableStream({
      start(controller) {
        function readA() {
          readerA.read().then(({done, value}) => {
            if (done) {
              readB();
              return;
            }
            controller.enqueue(value);
            readA();
          });
        }
        function readB() {
          readerB.read().then(({done, value}) => {
            if (done) {
              controller.close();
              return;
            }
            controller.enqueue(value);
            readB();
          });
        }
        readA();
      },
    });
  }

  async function readContent(stream) {
    const reader = stream.getReader();