Updated javadoc for persistRootOnly attribute.
Updated javadoc for persistRootOnly attribute.

To include information about task relinquishing identity.

Bug: 17618255
Change-Id: I94965fc213769b21ad70a22f3d3b603084054357

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