[This example](https://codesandbox.io/s/1zn2o513pq) presents a huge performance drop between React 16.2 and React 16.3.

In investigated it and noticed several things:

- Perfomance drop is only visible using development bundle
- This is not related to styled-components (a simple div presents the same problem)
- I tried to investigate in performance tab of Chrome dev tools and I noticed that I get React measures even without "?react_perf"
- React Tree Reconciliation seems very long, do not know why

It is not a big problem for me, but it looks weird, so I decided to [share it on Twitter](https://twitter.com/neoziro/status/979756579296817154),  then @gaearon [invited me to submit an issue about it](https://twitter.com/dan_abramov/status/980036013518139398).


}
  }
  function syncUpdates<A, B, C0, D, R>(
    fn: (A, B, C0, D) => R,
    a: A,
    b: B,
    c: C0,
    d: D,
  ): R {
    const previousExpirationContext = expirationContext;
    expirationContext = Sync;
    try {
      return fn(a, b, c, d);
    } finally {
      expirationContext = previousExpirationContext;
    }
  }
  
  
  
  let firstScheduledRoot: FiberRoot | null = null;
  let lastScheduledRoot: FiberRoot | null = null;
  let callbackExpirationTime: ExpirationTime = NoWork;
  let callbackID: number = -1;
  let isRendering: boolean = false;
  let nextFlushedRoot: FiberRoot | null = null;
  let nextFlushedExpirationTime: ExpirationTime = NoWork;
  let lowestPendingInteractiveExpirationTime: ExpirationTime = NoWork;
  let deadlineDidExpire: boolean = false;
  let hasUnhandledError: boolean = false;