Move reference processor and mirror::Reference to ObjPtr

Bug: 31113334

Test: test-art-host

Change-Id: I2c7c3dfd88ebf12a0de271436f8a7781f997e061
diff --git a/runtime/native/java_lang_ref_Reference.cc b/runtime/native/java_lang_ref_Reference.cc
index 95f6d51..bedca10 100644
--- a/runtime/native/java_lang_ref_Reference.cc
+++ b/runtime/native/java_lang_ref_Reference.cc
@@ -28,8 +28,8 @@
 static jobject Reference_getReferent(JNIEnv* env, jobject javaThis) {
   ScopedFastNativeObjectAccess soa(env);
   ObjPtr<mirror::Reference> ref = soa.Decode<mirror::Reference>(javaThis);
-  mirror::Object* const referent =
-      Runtime::Current()->GetHeap()->GetReferenceProcessor()->GetReferent(soa.Self(), ref.Ptr());
+  ObjPtr<mirror::Object> const referent =
+      Runtime::Current()->GetHeap()->GetReferenceProcessor()->GetReferent(soa.Self(), ref);
   return soa.AddLocalReference<jobject>(referent);
 }