GridLayoutManager: fix focus lost in fast layout

In fast layout,  if there is delta,  we unapplied delta first, which
may cause the detached focus child move outside visible area and it's
not added back at end of fast layout.  And another rare case  is
that child layout changes causing focused child being pushed outside
visible area.

Bug 19573463

Change-Id: Ib096bf68f57c32ce8d8ecd13621e0ab35719949e
1 file changed