With this change, the system process will put up a scrim in the
event keyguard crashes to protect underlying content.
It also adds permission checks to prevent unathorized access
through the binder APIs.
Cleaned up KeyguardTestActivity to build separately.
Removed unused resources.
Change-Id: I9e370c6bfb7dca68eae9eae304c815fb84a753d2
c0b676dcc2