SecurityException from Applet calling Thread.setPriority(int)

As of JDK 9 b120 the "Animator" demo applet throws an exception as follows :-
jdk9b120/bin/appletviewer example1.html
java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThread")
at java.security.AccessControlContext.checkPermission(java.base@9-ea/AccessControlContext.java:468)
at java.security.AccessController.checkPermission(java.base@9-ea/AccessController.java:894)
at java.lang.SecurityManager.checkPermission(java.base@9-ea/SecurityManager.java:541)
at sun.applet.AppletSecurity.checkAccess(java.desktop@9-ea/AppletSecurity.java:231)
at java.lang.Thread.checkAccess(java.base@9-ea/Thread.java:1488)
at java.lang.Thread.setPriority(java.base@9-ea/Thread.java:1185)
at Animator.init(Animator.java:299)
at sun.applet.AppletPanel.run(java.desktop@9-ea/AppletPanel.java:423)
at java.lang.Thread.run(java.base@9-ea/Thread.java:843)
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I am not sure of why, since I can't pinpoint what changed, but
can see that in AppletSecurity.java the call to
"currentAppletClassLoader()" returns null now .. which is
then interpreted as meaning the Thread (which is the applet's
own main thread), is not in its thread group ... and that
seems wrong .. and presumably inconsistent with all history
since 1995 since the applet has always made this call.