commit 1e2fa5e79fb5240cca20105508c2f7a49f8005b6
author Ben Kwa <kenobi@google.com> Tue Feb 02 23:00:02 2016 -0800
committer Ben Kwa <kenobi@google.com> Tue Feb 09 18:06:11 2016 +0000
tree 7892d63b21b0fba3e7742d69f062472345100081
parent ccdd08d37cc2b95da22941cc8fe80488d5d498e5

Implement PgUp/PgDn support.  (cherry-pick DO NOT MERGE)

- Clean up our LayoutManager code.  We actually only need a single
  layout manager, since a GridLayoutManager is a LinearLayoutManager,
  and list layout is simply grid layout with one column.  Make it so.

- Use the layout manager to compute item offsets for one page's worth of
  items.  Use that to implement page up/page down.

BUG=25195770

Change-Id: I23ddd5fd38532682e7f099b44e188d8c3fec02be
(cherry picked from commit 4d4bf9a21a16bae3497f94dbb558a2ede9d989ee)