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/interpreter/unstarted_runtime.cc b/runtime/interpreter/unstarted_runtime.cc
index eb8cdbc..89cbbe6 100644
--- a/runtime/interpreter/unstarted_runtime.cc
+++ b/runtime/interpreter/unstarted_runtime.cc
@@ -1619,9 +1619,9 @@
     uint32_t* args ATTRIBUTE_UNUSED, JValue* result) {
   ScopedObjectAccessUnchecked soa(self);
   if (Runtime::Current()->IsActiveTransaction()) {
-    result->SetL(soa.Decode<mirror::Object>(self->CreateInternalStackTrace<true>(soa)).Decode());
+    result->SetL(soa.Decode<mirror::Object>(self->CreateInternalStackTrace<true>(soa)).Ptr());
   } else {
-    result->SetL(soa.Decode<mirror::Object>(self->CreateInternalStackTrace<false>(soa)).Decode());
+    result->SetL(soa.Decode<mirror::Object>(self->CreateInternalStackTrace<false>(soa)).Ptr());
   }
 }