Sharesheet - 4->8 direct share expansion fix

The 4->8 expansion area can become stuck when the user is scrolling as
the list is rebuilt, say from a package changed event. Be more
specific about when we choose to lock this area.

Bug: 129979914
Test: Constantly scroll while sharesheet is loading
Change-Id: I969d628e1e420fd12133cef413dadf4f14ca75d7