Move mirror::ObjectArray to ObjPtr

Also reduce calls to ObjPtr::Ptr.

Bug: 31113334

Test: test-art-host -j32

Change-Id: I73e1b356972bb079b66332f00f7f07451601044e
diff --git a/runtime/native/java_lang_reflect_Executable.cc b/runtime/native/java_lang_reflect_Executable.cc
index e317c25..a0a6a12 100644
--- a/runtime/native/java_lang_reflect_Executable.cc
+++ b/runtime/native/java_lang_reflect_Executable.cc
@@ -38,7 +38,7 @@
     ObjPtr<mirror::Class> annotation_array_class =
         soa.Decode<mirror::Class>(WellKnownClasses::java_lang_annotation_Annotation__array);
     ObjPtr<mirror::ObjectArray<mirror::Object>> empty_array =
-        mirror::ObjectArray<mirror::Object>::Alloc(soa.Self(), annotation_array_class.Ptr(), 0);
+        mirror::ObjectArray<mirror::Object>::Alloc(soa.Self(), annotation_array_class, 0);
     return soa.AddLocalReference<jobjectArray>(empty_array);
   }
   return soa.AddLocalReference<jobjectArray>(annotations::GetAnnotationsForMethod(method));