RFR: 8262092: vmTestbase/nsk/jvmti/scenarios/hotswap/HS102/hs102t001/TestDescription.java SIGSEGV in memmove_ssse3

[Alex Menkov]

Class loading can happen on different threads, but HotSwap agent is not ready to this - classCount variable is used without any synchronization.
The fix adds synchronization for ClassFileLoadHook.

-------------

Commit messages:
 - Added synchronization for ClassFileLoadHook callback

Changes: https://git.openjdk.java.net/jdk/pull/3889/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3889&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262092
  Stats: 35 lines in 1 file changed: 22 ins; 7 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3889.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3889/head:pull/3889

PR: https://git.openjdk.java.net/jdk/pull/3889