<AWT Dev> [9] Review request for 8140311: SwingInterop crashes at window close

[Alexander Zvegintsev]

Hello,

please review the fix

http://cr.openjdk.java.net/~azvegint/jdk/9/8140311/00/

for the issue

https://bugs.openjdk.java.net/browse/JDK-8140311

This issue is only reproducible when a window using CWarningWindow.
After window close we cancel HidingTask in CWarningWindow at java level, 
however we do not cancel delayed execution of "perform" selector at 
native level.
At this point cached JNIEnv value becomes invalid, which is leading to 
crash.

-- 
Thanks,
Alexander.