Add back a helper pref that holds a system setting.

Change-Id: I7d8978829bde1f1dd15bf59f464557f64aa07beb

(cherry picked from commit 5a51eab743fd3c675c20e6662aa1da7969f2964b)
Add Buttons settings drawable

Change-Id: I8a684dafc823e580d855ed608130fd14f8684cd9

(cherry picked from commit 24de8f52e438ffeb9eda071fe066d71c3d00d1cb)