Rename ObjPtr::Decode to ObjPtr::Ptr

Done to prevent ambiguity with ScopedObjectAccess::Decode.

Bug: 31113334

Test: test-art-host
Change-Id: I07a2497cc9cf66386311798933547471987fc316
diff --git a/runtime/native/java_lang_ref_FinalizerReference.cc b/runtime/native/java_lang_ref_FinalizerReference.cc
index 08bcc38..1f03c7c 100644
--- a/runtime/native/java_lang_ref_FinalizerReference.cc
+++ b/runtime/native/java_lang_ref_FinalizerReference.cc
@@ -29,7 +29,7 @@
   ScopedFastNativeObjectAccess soa(env);
   ObjPtr<mirror::FinalizerReference> ref = soa.Decode<mirror::FinalizerReference>(javaThis);
   return Runtime::Current()->GetHeap()->GetReferenceProcessor()->MakeCircularListIfUnenqueued(
-      ref.Decode());
+      ref.Ptr());
 }
 
 static JNINativeMethod gMethods[] = {