Revert "Disable opaque JNI Ids for now."

We were incorrectly using a potentially out-of-date pointer to access
class object fields. This could cause segvs if the class object moves
during certain allocations relating to JNI id allocation.

This reverts commit 1be9c72dd49e7620dd76a8b9cef23d7cde0a6b01.

Reason for revert: Fixed issue with gcstress
Test: ./test.py --host --debuggable --gcstress
Bug: 134162467

Change-Id: I6ee7fc4485bbae6f0f1d4f4af0e8c2bc88bf4075
4 files changed