Fastpath some spread-call desugaring.

src/isolate-inl.h

Index: src/isolate-inl.h
diff --git a/src/isolate-inl.h b/src/isolate-inl.h
index 879e6e1a2baf68a5110f88917059852230a7894a..a148968b27151429ebd08ec26b0a547934e2ad3e 100644
--- a/src/isolate-inl.h
+++ b/src/isolate-inl.h
@@ -130,22 +130,27 @@ bool Isolate::IsArraySpeciesLookupChainIntact() {
 
   Cell* species_cell = heap()->species_protector();
   return species_cell->value()->IsSmi() &&
-         Smi::cast(species_cell->value())->value() == kArrayProtectorValid;
+         Smi::cast(species_cell->value())->value() == kProtectorValid;
 }
 
 bool Isolate::IsHasInstanceLookupChainIntact() {
   PropertyCell* has_instance_cell = heap()->has_instance_protector();
-  return has_instance_cell->value() == Smi::FromInt(kArrayProtectorValid);
+  return has_instance_cell->value() == Smi::FromInt(kProtectorValid);
 }
 
 bool Isolate::IsStringLengthOverflowIntact() {
   PropertyCell* has_instance_cell = heap()->string_length_protector();
-  return has_instance_cell->value() == Smi::FromInt(kArrayProtectorValid);
+  return has_instance_cell->value() == Smi::FromInt(kProtectorValid);
 }
 
 bool Isolate::IsFastArrayIterationIntact() {
   Cell* fast_iteration = heap()->fast_array_iteration_protector();
-  return fast_iteration->value() == Smi::FromInt(kArrayProtectorValid);
+  return fast_iteration->value() == Smi::FromInt(kProtectorValid);
+}
+
+bool Isolate::IsArrayIteratorLookupChainIntact() {
+  Cell* array_iterator_cell = heap()->array_iterator_protector();
+  return array_iterator_cell->value() == Smi::FromInt(kProtectorValid);
 }
 
 }  // namespace internal