[7u6] Request for approval for CR 7149062: [macosx] dock menu don't show available frames

[Anthony Petrov]

This is a back port of the same fix from JDK 8.

Bug: http://bugs.sun.com/view_bug.do?bug_id=7149062
Webrev: 
http://cr.openjdk.java.net/~anthony/7u6-9-windowListInDockMenu-7149062.0/
Review thread: 
http://mail.openjdk.java.net/pipermail/macosx-port-dev/2012-May/004140.html
Reviewers: Mike Swingler
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best regards,
Anthony