Add stale weak global unit test to jni_internal_test.
Add stale weak global unit test to jni_internal_test.

Prevents regressions related to:
https://code.google.com/p/android/issues/detail?id=63929

Change-Id: I4a3dbb2765523eac47e308fbdefa9558a38d346d

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