<AWT Dev> [8] Review request for 7175707: [macosx] PIT: 8 b43 Not running on AppKit thread issue again

[Alexander Scherbatiy]

bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7175707
webrev: http://cr.openjdk.java.net/~alexsch/7175707/webrev.00

The nativeGetNSWindowDisplayID_AppKitThread can be invoked both from the 
AppKitThread and not from the AppKitThread.
The fix invokes the GetNSWindowDisplayID_AppKitThread method on the 
AppKitThread in case if we are no on the AppKitThread.

Thanks,
Alexandr.