Cleanup element normalization logic

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index f4807a629700f91dc4344ecce14571a4f2a0313a..e39912b00d80d87044d98612c4caebabda2c8edc 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2437,7 +2437,9 @@ bool Isolate::IsFastArrayConstructorPrototypeChainIntact() {
     return cell_reports_intact;
   }
 
-  if (initial_array_proto->elements() != heap()->empty_fixed_array()) {
+  FixedArrayBase* elements = initial_array_proto->elements();
+  if (elements != heap()->empty_fixed_array() &&
+      elements != heap()->empty_slow_element_dictionary()) {
     DCHECK_EQ(false, cell_reports_intact);
     return cell_reports_intact;
   }
@@ -2448,7 +2450,10 @@ bool Isolate::IsFastArrayConstructorPrototypeChainIntact() {
     DCHECK_EQ(false, cell_reports_intact);
     return cell_reports_intact;
   }
-  if (initial_object_proto->elements() != heap()->empty_fixed_array()) {
+
+  elements = initial_object_proto->elements();
+  if (elements != heap()->empty_fixed_array() &&
+      elements != heap()->empty_slow_element_dictionary()) {
     DCHECK_EQ(false, cell_reports_intact);
     return cell_reports_intact;
   }