Track global cells as special side effects in GVN.

src/handles-inl.h

Index: src/handles-inl.h
diff --git a/src/handles-inl.h b/src/handles-inl.h
index 22bbd7cd7c13fc10a4645407317ea65debf05769..a25b4a2266c6e19cb939b3270e9a9f38faeb6649 100644
--- a/src/handles-inl.h
+++ b/src/handles-inl.h
@@ -97,7 +97,8 @@ bool Handle<T>::IsDereferenceAllowed(DereferenceCheckMode mode) const {
   if (!AllowHandleDereference::IsAllowed()) return false;
   if (mode == INCLUDE_DEFERRED_CHECK &&
       !AllowDeferredHandleDereference::IsAllowed()) {
-    // Accessing maps and internalized strings is safe.
+    // Accessing cells, maps and internalized strings is safe.
+    if (heap_object->IsCell()) return true;
     if (heap_object->IsMap()) return true;
     if (heap_object->IsInternalizedString()) return true;
     return !heap->isolate()->IsDeferredHandle(handle);