RFR: 8266857: PipedOutputStream.sink should be volatile

[Liam Miller-Cushon]

8266857: PipedOutputStream.sink should be volatile

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

Commit messages:
 - 8266857: PipedOutputStream.sink should be volatile

Changes: https://git.openjdk.java.net/jdk/pull/3960/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3960&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266857
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3960.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3960/head:pull/3960

PR: https://git.openjdk.java.net/jdk/pull/3960