ObjPtr<>-ify array allocations.

And remove some unnecessary calls to ObjPtr<>::Ptr().

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 31113334
Change-Id: Ie313980f7f23b33b0ccea4fa8d5131d643c59080
diff --git a/runtime/class_root.h b/runtime/class_root.h
index 5c78198..4aa9801 100644
--- a/runtime/class_root.h
+++ b/runtime/class_root.h
@@ -127,7 +127,7 @@
   ObjPtr<mirror::Class> klass =
       class_roots->GetWithoutChecks<kDefaultVerifyFlags, kReadBarrierOption>(index);
   DCHECK(klass != nullptr);
-  return klass.Ptr();
+  return klass;
 }
 
 template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier>