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_System.cc b/runtime/native/java_lang_System.cc
index 8b9d0c7..f3756a2 100644
--- a/runtime/native/java_lang_System.cc
+++ b/runtime/native/java_lang_System.cc
@@ -62,12 +62,12 @@
   // Make sure source and destination are both arrays.
   ObjPtr<mirror::Object> srcObject = soa.Decode<mirror::Object>(javaSrc);
   if (UNLIKELY(!srcObject->IsArrayInstance())) {
-    ThrowArrayStoreException_NotAnArray("source", srcObject.Decode());
+    ThrowArrayStoreException_NotAnArray("source", srcObject.Ptr());
     return;
   }
   ObjPtr<mirror::Object> dstObject = soa.Decode<mirror::Object>(javaDst);
   if (UNLIKELY(!dstObject->IsArrayInstance())) {
-    ThrowArrayStoreException_NotAnArray("destination", dstObject.Decode());
+    ThrowArrayStoreException_NotAnArray("destination", dstObject.Ptr());
     return;
   }
   mirror::Array* srcArray = srcObject->AsArray();