ART: Use ObjPtr for GetSuperClass

Bug: 37224696
Test: mmma art
Test: m test-art-host
Change-Id: If55db6e26bb1bb05a13c59b849bed17839fca6cf
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index eddc84b..cbe377e 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -624,7 +624,7 @@
 
   template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags,
            ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
-  ALWAYS_INLINE Class* GetSuperClass() REQUIRES_SHARED(Locks::mutator_lock_);
+  ALWAYS_INLINE ObjPtr<Class> GetSuperClass() REQUIRES_SHARED(Locks::mutator_lock_);
 
   // Get first common super class. It will never return null.
   // `This` and `klass` must be classes.