JDK-8022853 added 3 methods to the Unsafe API in order to provide supported entry points for JVMCI to retrieve some VM internal data. A later implementation change of JVMCI which was required to handle class redefinition properly made 2 of these methods unnecessary:

    public native Class<?> getJavaMirror(long metaspaceKlass);
    public native long getKlassPointer(Object o);

Since these methods only exist in JDK 9 we can, and should, just remove them.