I've observed that when React's profiling mode is enabled, updating the profiling fields [here](https://github.com/facebook/react/blob/1d25aa5787d4e19704c049c3cfa985d3b5190e0d/packages/react-reconciler/src/ReactProfilerTimer.js#L46) and [here](https://github.com/facebook/react/blob/1d25aa5787d4e19704c049c3cfa985d3b5190e0d/packages/react-reconciler/src/ReactProfilerTimer.js#L69-L71) during the _render_ phase seems to cause a significant deopt in [`getHostSibling`](https://github.com/facebook/react/blob/1d25aa5787d4e19704c049c3cfa985d3b5190e0d/packages/react-reconciler/src/ReactFiberCommitWork.js#L858-L898) during the _commit_ phase for Chrome only. (Neither Safari nor Firefox seem to be affected by this.)

I have created a repro case with inline annotations here:
https://github.com/bvaughn/react-profiling-v8-deopt-repro#about-this-repro-case

(Note that the above repo is private. Please tag me here if you need access.)
key: null | string,
  
  
  elementType: any,
  
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  return: Fiber | null,
  
  child: Fiber | null,
  sibling: Fiber | null,
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  ref: null | (((handle: mixed) => void) & {_stringRef: ?string}) | RefObject,
  
  pendingProps: any, 
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  updateQueue: UpdateQueue<any> | null,