[8u]: 8136592: [TEST_BUG] Fix 2 platform-specific closed regtests for jigsaw

[Hohensee, Paul]

Please review this test-only backport. The JBS issue is private, so I can’t create a backport issue. We’ll have to rely on hg-updater when pushed, and maintainer approval will have to be on the list.

Original patch: http://hg.openjdk.java.net/jdk-updates/jdk9u/jdk/rev/ddc8bbf88d36
8u webrev: http://cr.openjdk.java.net/~phh/8136592/webrev.8u.jdk.02/

The @modules attributes have been removed, and implicit casts have been replaced by explicit ones to XEmbedCanvasPeer, FramePeer, and ListPeer. The first two required importing sun.awt.X11.*.

The two new tests pass.

Thanks,
Paul