Explicitly set highWaterMark to 0 for ReadableStream (#24641)

* Explicitly set highWaterMark to 0 for ReadableStreams This is because not all streaming implementations respect the default behavior of settings highWaterMark to 0 for byte streams. Being explicit guarantees the intended behavior across runtimes. * Remove size methods and add FlowFixMe instead

Author: jplhomer

packages/react-dom/src/server/ReactDOMFizzServerBrowser.js

@@ -53,15 +53,19 @@ function renderToReadableStream(
  });
 
  function onShellReady() {
- const stream: ReactDOMServerReadableStream = (new ReadableStream({
- type: 'bytes',
- pull(controller) {
- startFlowing(request, controller);
+ const stream: ReactDOMServerReadableStream = (new ReadableStream(
+ {
+ type: 'bytes',
+ pull(controller) {
+ startFlowing(request, controller);
+ },
+ cancel(reason) {
+ abort(request);
+ },
  },
- cancel(reason) {
- abort(request);
- },
- }): any);
+ // $FlowFixMe size() methods are not allowed on byte streams.
+ {highWaterMark: 0},
+ ): any);
  // TODO: Move to sub-classing ReadableStream.
  stream.allReady = allReady;
  resolve(stream);

packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js

@@ -33,16 +33,20 @@ function renderToReadableStream(
  options ? options.onError : undefined,
  context,
  );
- const stream = new ReadableStream({
- type: 'bytes',
- start(controller) {
- startWork(request);
+ const stream = new ReadableStream(
+ {
+ type: 'bytes',
+ start(controller) {
+ startWork(request);
+ },
+ pull(controller) {
+ startFlowing(request, controller);
+ },
+ cancel(reason) {},
  },
- pull(controller) {
- startFlowing(request, controller);
- },
- cancel(reason) {},
- });
+ // $FlowFixMe size() methods are not allowed on byte streams.
+ {highWaterMark: 0},
+ );
  return stream;
 }