[9] Review Request: 8143256 The build is broken after JDK-8081411

[Sergey Bylokhov]

Hello.
Please review the fix for jdk9.
The build is broken after JDK-8081411. The code on unix is not updated 
to use interface SynthIcon instead of class.

Bug: https://bugs.openjdk.java.net/browse/JDK-8143256
Webrev can be found at: http://cr.openjdk.java.net/~serb/8143256/webrev.01

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Best regards, Sergey.