Fix jclass read barrier in GenericJNI.

The GcRoot<>::Read<kWithReadBarrier>() does not update
the GcRoot<>::root_ which we need to do.

Test: m
Bug: 172332525
Bug: 181249330
Change-Id: I9886c6f23339e39588c885d7b1e2557abae8d027
1 file changed