[9] Review Request: 8166673 The new implementation of Robot.waitForIdle() may hang

[Sergey Bylokhov]

Hello.

Please review the fix for jdk9.
The SunToolkit.waitForIdle() uses string literal for synchronization, 
which means some code (intentionally or not) can hang Robot.waitForIdle.

Bug: https://bugs.openjdk.java.net/browse/JDK-8166673
Webrev can be found at: http://cr.openjdk.java.net/~serb/8166673/webrev.00

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Best regards, Sergey.