Fix ANR which could occur for collection widgets with very large items

-> We cache RemoteViews which populate the AdapterViews, but only
   up to a total memory amount of 2MB. The remainder of the cache
   is pruned out. If _every_ item is greater than 2MB, we were failing
   to prune the last item, leaving the framework in a loop on a bg
   thread, but holding a lock required by the main thread.

Change-Id: I0574a25a59ebec6586ae223fff6605c0fee953c3