Disallow direct subclasses of java.lang.ref.Reference.
Disallow direct subclasses of java.lang.ref.Reference.

More extra-linguistic bullshit.

Change-Id: Ib2c5328e5d934a06d5df8902d4b10ad28c458278

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst