Mark PDB identifier as SystemApi
Mark PDB identifier as SystemApi

Had already marked the API itself as system api, just not
the Context.BLAH id. Also update the javadoc as it doesn't
return an FD anymore.

Change-Id: Ic8a5b8c75b0ba0bdf4ad26cf33d5f87eea568376

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base