[8u] Request for approval - 8145539: (coll) AbstractMap.keySet and .values should not be volatile

[Aleksey Shipilev]

Hi,

Please approve and sponsor this simple backport for an old (yet
important) performance issue in collections:
  https://bugs.openjdk.java.net/browse/JDK-8145539

The fix was in jdk9/dev for at least 4 days now.

JDK 9 Changeset:
  http://hg.openjdk.java.net/jdk9/dev/jdk/rev/ce72c7641f38

JDK 9 review thread:

http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-December/037674.html

Patch applies with little fuzz after unshuffling. For the record, this
is the clean patch against current 8u:
  http://cr.openjdk.java.net/~shade/8145539/8145539-8u.patch

Testing: builds and runs fine on Linux x86_64, microbenchmark
improvements are the same as in JDK 9.

Thanks,
-Aleksey