Allow subclasses to override bindPreferences().

Allows them to modify adapter behaviour.

Change-Id: I6767e3988740b674fbdf40a903cd2ef3949ca7db
Themes: Style, boot animation, and wallpaper previews

Change-Id: I2b367bf5336c03f2a4972a05b68922065cd4a701
Fix possible NPE in SyncHandler.onBootCompleted()

If onBootCompleted() was called a second time, it would have throw a
NullPointerException since the queue object would have already been
set to null by the previous call. This commit just makes such an
object behave as an empty queue instead of throwing the exception.

Change-Id: I7ef82ba1e2504ceb0a2c11694d32f0588db7d0af