This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
}
    if (node === workInProgress) {
      return;
    }
    while (node.sibling === null) {
      if (node.return === null || node.return === workInProgress) {
        return;
      }
      node = node.return;
    }
    node.sibling.return = node.return;
    node = node.sibling;
  }
}
function findLastContentRow(firstChild: null | Fiber): null | Fiber {
  
  
  
  
  
  
  
  let row = firstChild;
  let lastContentRow: null | Fiber = null;
  while (row !== null) {
    const currentRow = row.alternate;
    
    if (currentRow !== null && findFirstSuspended(currentRow) === null) {
      lastContentRow = row;
    }