This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
workInProgress.childLanes = current.childLanes;
    workInProgress.lanes = current.lanes;
    workInProgress.child = current.child;
    workInProgress.subtreeFlags = NoFlags;
    workInProgress.deletions = null;
    workInProgress.memoizedProps = current.memoizedProps;
    workInProgress.memoizedState = current.memoizedState;
    workInProgress.updateQueue = current.updateQueue;
    
    workInProgress.type = current.type;
    
    
    const currentDependencies = current.dependencies;
    workInProgress.dependencies =
      currentDependencies === null
        ? null
        : {
            lanes: currentDependencies.lanes,
            firstContext: currentDependencies.firstContext,
          };
    if (enableProfilerTimer) {
      
      
      workInProgress.selfBaseDuration = current.selfBaseDuration;
      workInProgress.treeBaseDuration = current.treeBaseDuration;
    }
  }
  return workInProgress;
}
export function createHostRootFiber(