Some system apps are more system than others

"signatureOrSystem" permissions are no longer available to all apps
residing en the /system partition.  Instead, there is a new /system/priv-app
directory, and only apps whose APKs are in that directory are allowed
to use signatureOrSystem permissions without sharing the platform cert.
This will reduce the surface area for possible exploits of system-
bundled applications to try to gain access to permission-guarded
operations.

The ApplicationInfo.FLAG_SYSTEM flag continues to mean what it is
says in the documentation: it indicates that the application apk was
bundled on the /system partition.  A new hidden flag FLAG_PRIVILEGED
has been introduced that reflects the actual right to access these
permissions.

At some point the "system" permission category will be
renamed to "privileged".

Bug 8765951

Change-Id: I6f0fd9cdb9170e076dfc66d83ecea76f8dd7335d
16 files changed