RFR(XXS) : 8160025 : compiler/testlibrary/uncommontrap/Verifier doesn't close FileReader

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev/8160025/webrev.00/
> 4 lines changed: 3 ins; 0 del; 1 mod;
Hi all,

could you please review this tiny fix adds try-w/-resources to ensure that new created FileReader will be closed?

because of this bug, compiler/uncommontrap/TestUnstableIfTrap.java fails on windows during 8132920 integration. we haven't see this before 8132920, because Verifier was run in othervm mode, so JVM which run it was always closed before clean-up phase.

webrev: http://cr.openjdk.java.net/~iignatyev/8160025/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8160025
testing: compiler/uncommontrap/TestUnstableIfTrap.java on mac and windows (running)

Thanks,
— Igor