Don't ignore model changes when the ListView scroll position changes.

Don't ignore model changes when the ListView scroll position changes.

If there are pending changes when the ListView viewport changes then
do a full layout instead of a refill.  Likewise for GridView and when
animations finish or the cacheBuffer size changes.

Change-Id: I57a2b01fee5729381558af366dad24ba26c223ef
Reviewed-by: Bea Lam <bea.lam@nokia.com>