If the delegate's size changes in componentComplete and all
items are flicked out of view, an incorrect jump calculation
in addVisibleItems() resulted in a new delegate being created
in the wrong position, and retriggering the jump calculation,
which resulted in a new delegate being created in the wrong
position, and retriggering the jump...

Also fixed currentItem visibility.

Change-Id: Iad5f211c4fc5eed9c009d51a0ce3b58181a7b36e
Reviewed-by: Bea Lam <bea.lam@nokia.com>