[9] Review Request for 6921687: Mnemonic disappears after repeated attempts to open menu items using mnemonics

[Semyon Sadetsky]

Hello,

Please review JDK9 fix.
webrev: 
http://cr.openjdk.java.net/~alexsch/semyon-sadetsky/6921687/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-6921687

Thanks!
--Semyon