Do not penalize performance when --harmony-species is off

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index c81afcc0e744226b626a9ba497af6199aa6ec5ef..fe42e162177f5574120b85243486f0d865fef11f 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2546,6 +2546,7 @@ bool Isolate::IsFastArrayConstructorPrototypeChainIntact() {
 }
 
 bool Isolate::IsArraySpeciesLookupChainIntact() {
+  if (!FLAG_harmony_species) return true;
   // Note: It would be nice to have debug checks to make sure that the
   // species protector is accurate, but this would be hard to do for most of
   // what the protector stands for:
@@ -2564,6 +2565,7 @@ bool Isolate::IsArraySpeciesLookupChainIntact() {
 }
 
 void Isolate::InvalidateArraySpeciesProtector() {
+  if (!FLAG_harmony_species) return;
   DCHECK(factory()->species_protector()->value()->IsSmi());
   DCHECK(IsArraySpeciesLookupChainIntact());
   PropertyCell::SetValueWithInvalidation(