Add DPAD support to capture window

This CL adds DPAD support for capture screen gestures, in particular
to mode switcher and to filmstrip. Left goes to mode switcher and again
toggles it off; right goes to filmstrip.

A followon CL will add additional filmstrip calls that control gestures
within the filmstrip itself, namely navigation between items and hiding.

Bug: 13589550
Change-Id: I7b6a7a37c5be8137c2503244dc178284139594dd
3 files changed