<AWT Dev> [8] Request for review: JDK-8022512 JLightweightFrame: the content pane should be transparent

[Anton V. Tarasov]

Please, review a fix.

jira: https://bugs.openjdk.java.net/browse/JDK-8022512
webrev: http://cr.openjdk.java.net/~ant/JDK-8022512/webrev.0/

Both JLF and its Content Pane are "transparent" to the client app, e.g. 
SwingNode, in terms of functionality. They should be physically 
transparent as well, in order to support translucent Swing content. This 
is the case for JLF, but not for the Content Pane yet.

Thanks,
Anton.