@Override
    protected void addChange(int start1, int start2, int end1, int end2) {
      Diff.Change change = new Diff.Change(start1, start2, end1 - start1, end2 - start2, null);
      if (myLastChange != null) {
        myLastChange.link = change;
      }
      else {
        myFirstChange = change;
      }
      myLastChange = change;
    }
@Override
    protected void addChange(int start1, int start2, int end1, int end2)