Fix Icon size in DocumentsUI

For XXHDPI devices if you go into Settings/Display and Notification light and select a custom value (application) you will see a GIANT icon.

Before - http://i.imgur.com/DRkua3T.png

After - http://i.imgur.com/f7xW4tY.png

Change-Id: Ia355bddc515906134c8b3b4e67d381aaacceec78
[1/2] SystemUI: Add brightness slider to notification drawer

adds a brightness slider below the expanded statusbar header and
(if enabled) quick settings ribbons

also wrap an if around gesture recorder in the fling methods, only
call them if DEBUG is enabled.

Change-Id: I65077f5ddb20aa9f13813eedfaa0cb09a667eb88