Fix tracking of computed fields when field type tracking is disabled.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index ba5280e7e796d960854f6cb636404764ef2997b4..6a7931554baf321e3e212337a482a713864d3b3e 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -63,8 +63,8 @@ namespace internal {
 
 Handle<HeapType> Object::OptimalType(Isolate* isolate,
                                      Representation representation) {
+  if (representation.IsNone()) return HeapType::None(isolate);
   if (FLAG_track_field_types) {
-    if (representation.IsNone()) return HeapType::None(isolate);
     if (representation.IsHeapObject() && IsHeapObject()) {
       // We can track only JavaScript objects with stable maps.
       Handle<Map> map(HeapObject::cast(this)->map(), isolate);