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.)
const fiber = createFiber(HostPortal, pendingProps, portal.key, mode);
  fiber.expirationTime = expirationTime;
  fiber.stateNode = {
    containerInfo: portal.containerInfo,
    pendingChildren: null, // 
    implementation: portal.implementation,
  };
  return fiber;
}
// Used for stashing WIP properties to replay failed work in DEV.
export function assignFiberPropertiesInDEV(
  target: Fiber | null,
  source: Fiber,
): Fiber {
  if (target === null) {
    // 
    // 
    target = createFiber(IndeterminateComponent, null, null, NoContext);
  }
  // 
  // 
  // 
  // 
  // 
  target.tag = source.tag;
  target.key = source.key;
  target.elementType = source.elementType;
  target.type = source.type;
  target.stateNode = source.stateNode;
  target.return = source.return;