[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).


return !!(Component.prototype && Component.prototype.isReactComponent);
}
export function createWorkInProgress(
  current: Fiber,
  pendingProps: any,
  expirationTime: ExpirationTime,
): Fiber {
  let workInProgress = current.alternate;
  if (workInProgress === null) {
    
    
    
    
    
    workInProgress = createFiber(
      current.tag,
      pendingProps,
      current.key,
      current.mode,
    );
    workInProgress.type = current.type;
    workInProgress.stateNode = current.stateNode;
    if (__DEV__) {
      
      workInProgress._debugID = current._debugID;
      workInProgress._debugSource = current._debugSource;