[8u20] Request for approval: 8031425 - Two langtools/javac tests fail by timeout on Windows

[Alexander Zuev]

Please approve the backport of the following issue to the 8u20.

Bug: https://bugs.openjdk.java.net/browse/JDK-8031425
Fix pushed into jdk9 as: 
http://hg.openjdk.java.net/jdk9/dev/langtools/rev/6f773742b20f
Fix applies without an issue to 
http://hg.openjdk.java.net/jdk8u/jdk8u-dev/langtools
Webrev is available at: http://cr.openjdk.java.net/~kizune/8031425/webrev.00

/Alex