function getRowLabel(diffs) {
  if (!diffs.length) return 'no change';

  if (diffs.some(diff => diff.type === 'itemAddition')) return 'added';
  if (diffs.some(diff => diff.type === 'itemRemoval')) return 'removed';

  const itemDeltaDiffs = diffs.filter(
    /** @return {diff is LHCI.NumericItemAuditDiff} */ diff => diff.type === 'itemDelta'
  );

  // All the diffs were worse, it's "worse".
  if (itemDeltaDiffs.every(diff => diff.compareValue > diff.baseValue)) return 'worse';
  // All the diffs were better, it's "better".
  if (itemDeltaDiffs.every(diff => diff.compareValue < diff.baseValue)) return 'better';
  // The item had diffs but some were better and some were worse, so we can't decide.
  if (itemDeltaDiffs.length) return 'ambiguous';

  return 'no change';
}
Given the array of diffs for a particular row, determine its label.

@param {Array<LHCI.AuditDiff>} diffs
@return {RowLabel}