[8u20] request for approval to backport JDK-8040822: Duplicated notifications can be sent to TaskListener

[Jan Lahoda]

Hello,

I'd like to ask for an approval to backport fix for:

Bug: https://bugs.openjdk.java.net/browse/JDK-8040822
Backport bug: https://bugs.openjdk.java.net/browse/JDK-8042817
jdk9 fix: http://hg.openjdk.java.net/jdk9/dev/langtools/rev/da8d9f8995d1

The fix applies cleanly to: 
http://hg.openjdk.java.net/jdk8u/jdk8u-dev/langtools

Thanks,
    Jan