GitLab

- Updated WallpaperChooser to use FragmentDialogs
- Backwards compatible with old WallpaperChooser
  UI on non XLarge screens
- There is a known bug with AlertDialogs (b/3225529)
  that prevents an AlertDialog to expand to fit its
  content. The squishing of the GridView is caused
  by that bug.

Change-Id: I49381aab4aa24362e8c92da284797fce0e63823c