Supports extra layout space

When layout reordering aligned focused item,  extra space is
needed during prelayout for filling.  However there is no
general solution now based on REMOVE/CHANGE flag of ViewHolder.

This CL is a case-by-case solution allows extra item to be added in
invisble area so that item animator can animate slide-in instead of
fade-in.

b/21949401

Change-Id: Ic78a0d639f387a0bf319fcc504b8401262148a0b
3 files changed