RecyclerView scroll callback fix for 0 to 1

This CL fixes a bug in RecyclerView where it would not call
the scroll callbacks if the number of children changed
from 0 to 1 or 1 to 0.

Bug: 29445923
Change-Id: I4ec6fca71ca4800d17b3cc703b8a72b4b180032f
2 files changed