title: systemLayoutSizeFittingSize: returns different results on different iOS versions
body: <p>I have a <code>UITableView</code> with a prototype cell, whose height I am calculating using the following code:</p>
  
  <pre><code>- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
  {
      UITableViewCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath];
      [cell layoutIfNeeded];
      CGSize size = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
      return size.height + 1;
  }
  </code></pre>
  
  <p>The cell I'm dequeuing inside <code>cellForRowAtIndexPath</code> only has a <code>UILabel</code> in it and I'm setting an NSAttributedString as its text.</p>
  
  <p>The problem is, when I run this on a iOS 7.1 simulator, everything works perfect. However, when I run it on a iOS 8.4 simulator, this returns a larger height so there is excessive space on the bottom of the cell. What might be causing this? Any comment or suggestion would be appreciated.</p>