Function updateTextNode

docs/external/js/react-dom.development.js:13682–13694

(returnFiber, current, textContent, expirationTime)

    }

    function updateTextNode(returnFiber, current, textContent, expirationTime) {
      if (current === null || current.tag !== HostText) {
        // Insert
        var created = createFiberFromText(textContent, returnFiber.mode, expirationTime);
        created.return = returnFiber;
        return created;
      } else {
        // Update
        var existing = useFiber(current, textContent);
        existing.return = returnFiber;
        return existing;
      }
    }

    function updateElement(returnFiber, current, element, expirationTime) {
      if (current !== null) {