Batched state changes are not flushed if the promise code changes the DOM (= attaching an iframe). Reproduceable with Safari.

React version: 18.1.0

## Steps To Reproduce

1. Open [codepen](https://codepen.io/kh-viewar/pen/wvpVLxM) with Safari.
2. Click "Upload"
3. => "Spinner" text does not render while Promise is in pending

Link to code example:

https://codepen.io/kh-viewar/pen/wvpVLxM

## The current behavior

State changes are not executed.

## The expected behavior

State should change to true and render spinner component. After promise is resolved (2 seconds timeout), state should switch back to false and spinner component should unmount.

## Original discussion

https://github.com/facebook/react/issues/24365
(fiber.mode & ConcurrentMode) === NoMode &&
       
      !(__DEV__ && ReactCurrentActQueue.isBatchingLegacy)
    ) {
       
       
       
       
       
      resetRenderTimer();
      flushSyncCallbacksOnlyInLegacyMode();
    }
  }
  return root;
}
export function scheduleInitialHydrationOnRoot(
  root: FiberRoot,
  lane: Lane,
  eventTime: number,
) {
   
   
   
  
   
   
   
   
   
  const current = root.current;