Use check mark to indicate the applied wallpaper

Spec:
  https://screenshot.googleplex.com/8fCqWYnxXNgwbAR.png
  https://www.figma.com/file/OG3c0WuO6IWtKn7yZ5IQCw/BC-x-Next-Wallpaper-%26-style?node-id=6949%3A39971

Result:
  2 columns: https://screenshot.googleplex.com/BAkYSbNU3dVhjBr.png
  3 columns: https://screenshot.googleplex.com/4LR6VBuMA3qhJfS.png

Bug: 192415835
Test: manual
Change-Id: Ic051b54b8cbf84def8250c357dc7f92d3942221f
6 files changed