<AWT Dev> [9] Review Request: 8038765 [macosx] Toolkit.sync should be implemented

[Sergey Bylokhov]

Hello.
Please review the fix for jdk 9.
In the fix Toolkit.sync() is implemented in the same way as on other 
platforms. Note that on OSX we need additional step to flush the native 
selectors queue, because all our rendering was done to offscreen texture.

Bug: https://bugs.openjdk.java.net/browse/JDK-8038765
Webrev can be found at: http://cr.openjdk.java.net/~serb/8038765/webrev.00

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Best regards, Sergey.