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/indirect_reference_table-inl.h b/runtime/indirect_reference_table-inl.h
index 9673bd9..2128f8c 100644
--- a/runtime/indirect_reference_table-inl.h
+++ b/runtime/indirect_reference_table-inl.h
@@ -111,12 +111,12 @@
   if (serial_ == kIRTPrevCount) {
     serial_ = 0;
   }
-  references_[serial_] = GcRoot<mirror::Object>(obj.Ptr());
+  references_[serial_] = GcRoot<mirror::Object>(obj);
 }
 
 inline void IrtEntry::SetReference(ObjPtr<mirror::Object> obj) {
   DCHECK_LT(serial_, kIRTPrevCount);
-  references_[serial_] = GcRoot<mirror::Object>(obj.Ptr());
+  references_[serial_] = GcRoot<mirror::Object>(obj);
 }
 
 }  // namespace art