[7u6] Review request for 7160293 [macosx] FileDialog appears on secondary display

[Dmitry Cherepanov]

This is a direct back port of the fix to jdk7u6.

Bug: http://bugs.sun.com/view_bug.do?bug_id=7160293

Webrev: http://cr.openjdk.java.net/~dcherepanov/7160293/7u6/webrev.0/

Thanks,
Dmitry