8004141: UnsafeStaticFieldAccessorImpl#base should be final

Reviewed-by: chegar, alanb
Contributed-by: peter.levart@gmail.com

src/share/classes/sun/reflect/UnsafeStaticFieldAccessorImpl.java

@@ -43,7 +43,7 @@ abstract class UnsafeStaticFieldAccessorImpl extends UnsafeFieldAccessorImpl {
                                           new String[] { "base" });
     }
 
-    protected Object base; // base
+    protected final Object base; // base
 
     UnsafeStaticFieldAccessorImpl(Field field) {
         super(field);