RFR 6471769: Error: assert(_cur_stack_depth == count_frames(), "cur_stack_depth out of sync")

[serguei.spit...@oracle.com]

Please, review the fix for:
  https://bugs.openjdk.java.net/browse/JDK-6471769

Open webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/hotspot/6471769-JVMTI-DEPTH.1

Summary:

  This is another Test Stabilization issue.
  The fix is very similar to other JVMTI stabilization fixes.
  It is to use safepoints for updating the PopFrame data instead of 
relying on the
  suspend equivalent condition mechanism 
(JvmtiEnv::is_thread_fully_suspended())
  which is not adequate from the reliability point of view.

Testing:
  In progress: nsk.jvmti, nsk.jdi, nsk.jdwp, JTreg com/sun/jdi


Thanks,
Serguei