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/mirror/class-inl.h b/runtime/mirror/class-inl.h
index 62c583b..14bd243 100644
--- a/runtime/mirror/class-inl.h
+++ b/runtime/mirror/class-inl.h
@@ -655,7 +655,7 @@
   return GetFieldObject<String>(OFFSET_OF_OBJECT_MEMBER(Class, name_));
 }
 
-inline void Class::SetName(String* name) {
+inline void Class::SetName(ObjPtr<String> name) {
   if (Runtime::Current()->IsActiveTransaction()) {
     SetFieldObject<true>(OFFSET_OF_OBJECT_MEMBER(Class, name_), name);
   } else {