ObjPtr<>-ify ArtMethod and mirror::Method.

And clean up some forgotten things after old CLs.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 31113334
Change-Id: I8af0e845c24d674d0efab21d80c29949b1cc0593
diff --git a/openjdkjvmti/ti_method.cc b/openjdkjvmti/ti_method.cc
index 9f9dace..87d832c 100644
--- a/openjdkjvmti/ti_method.cc
+++ b/openjdkjvmti/ti_method.cc
@@ -384,7 +384,7 @@
   // Note: No GetInterfaceMethodIfProxy, we want to actual class.
 
   art::ScopedObjectAccess soa(art::Thread::Current());
-  art::mirror::Class* klass = art_method->GetDeclaringClass();
+  art::ObjPtr<art::mirror::Class> klass = art_method->GetDeclaringClass();
   *declaring_class_ptr = soa.AddLocalReference<jclass>(klass);
 
   return ERR(NONE);