RC: option to toggle dimming of the notification shade (2/2) - picked from Xylon rom

    Allow the user to enable/disable dimming of the notification shade
    pulldown. Check isHighEndGfx() to respect the default setting that
    the device currently supports.

    Users on low-end device may want to have this feature, while users
    on high-end devices may want to disable it (possible battery life
    savings and what not).

    Change-Id: I661254ec7ae1548707d94f5d41efe877554c6023