title: UICollectionView: How to get item size for a specific item after setting them in delegate method
body: <p>I am fiddling with the new UICollectionView and the UICollectionViewLayout classes. I have created a custom layout, subclassing UICollectionViewFlowLayout. </p>
  
  <p>My cell sizes are changing dynamically and I set the item sizes using the delegate method below</p>
  
  <pre><code>- (CGSize)collectionView:(UICollectionView *)collectionView
                    layout:(UICollectionViewLayout*)collectionViewLayout
    sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
  
        NSLog(@"SETTING SIZE FOR ITEM AT INDEX %d", indexPath.row);
        return CGSizeMake(80, 80);
  }
  </code></pre>
  
  <p>Now, under the prepareLayout method of my custom UICollectionViewFlowLayout class, I need to access these size variables so that I can make calculations how to place them and cache them for layoutAttributesForItemAtIndexPath.</p>
  
  <p>However, I can't seem to find any property under UICollectionView or UICollectionViewFlowLayout to reach the custom item sizes I set in the delegate method. </p>