title: UITableView scrolls to top when reloading cells with changing cell heights
body: <p>I have a table view which contains a placeholders while it loads in images. When the image is loaded, I call <code>reloadRowsAtIndexPaths:withRowAnimation:</code>. At this point, the cell changes height, based on the size of the image. When that happens, I want the table view's content offset to remain in place, and for the cells below to be pushed further down, as you might imagine.</p>
  
  <p>The effect I'm getting instead is that the scroll view scrolls back to the top. I'm not sure why this is, and I can't seem to prevent it. Putting <code>beginUpdates()</code> before and <code>endUpdates()</code>after the <code>reloadRows</code> line has no effect.</p>
  
  <p>I am using <code>estimatedRowHeight</code>, as is needed as my table view can potentially have hundreds of rows of different heights. I am also implementing <code>tableView:heightForRowAtIndexPath:</code>.</p>
  
  <p>EDIT: I've set up a demo project to test this, and admittedly I can't get the demo project to reproduce this effect. I'll keep working at it.</p>