@Nullable
  private static List<DiffFragment> dropWholeChangedFragments(@Nullable List<DiffFragment> fragments, int length1, int length2) {
    if (fragments != null && fragments.size() == 1) {
      DiffFragment diffFragment = fragments.get(0);
      if (diffFragment.getStartOffset1() == 0 &&
          diffFragment.getStartOffset2() == 0 &&
          diffFragment.getEndOffset1() == length1 &&
          diffFragment.getEndOffset2() == length2) {
        return null;
      }
    }
    return fragments;
  }
@Nullable
  private static List<DiffFragment> dropWholeChangedFragments(@Nullable List<DiffFragment> fragments, int length1, int length2)