[7u6] Review request for 7181027: [macosx] Unable to use headless mode

[Leonid Romanov]

Hi,
Please review a fix for 7181027: [macosx] Unable to use headless mode. The problem here is that for headless mode  "java.awt.graphicsenv" system property should be CGraphicsEnvironment because the way GraphicsEnvironment.createGE() method works: it first instantiates GraphicsEnvironment instance and then wraps it with HeadlessGraphicsEnvironment if in headless mode. This means twe can't use java.awt.graphicsenv property to determine whether we are in headless mode or not. So, I've replaced it with a toolkit check: if it's HToolkit, then we are in headless.  

Bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7181027
Webrev: http://cr.openjdk.java.net/~leonidr/7181027/webrev.00/

Thanks,
Leonid.