Don't internalize names that are array indexes since they aren't used for lookup (the index is)

src/lookup.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_LOOKUP_H_
 #define V8_LOOKUP_H_
 
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects.h"
@@ skipping 109 matching lines @@
         initial_holder_(holder_),
         number_(DescriptorArray::kNotFound) {
     // kMaxUInt32 isn't a valid index.
     DCHECK_NE(kMaxUInt32, index_);
     Next();
   }
 
   static LookupIterator PropertyOrElement(
       Isolate* isolate, Handle<Object> receiver, Handle<Name> name,
       Configuration configuration = DEFAULT) {
-    name = isolate->factory()->InternalizeName(name);
     uint32_t index;
-    LookupIterator it =
-        name->AsArrayIndex(&index)
-            ? LookupIterator(isolate, receiver, index, configuration)
-            : LookupIterator(receiver, name, configuration);
-    it.name_ = name;
-    return it;
+    if (name->AsArrayIndex(&index)) {
+      LookupIterator it =
+          LookupIterator(isolate, receiver, index, configuration);
+      it.name_ = name;
+      return it;
+    }
+    return LookupIterator(receiver, name, configuration);
   }
 
   static LookupIterator PropertyOrElement(
       Isolate* isolate, Handle<Object> receiver, Handle<Name> name,
       Handle<JSReceiver> holder, Configuration configuration = DEFAULT) {
-    name = isolate->factory()->InternalizeName(name);
     uint32_t index;
-    LookupIterator it =
-        name->AsArrayIndex(&index)
-            ? LookupIterator(isolate, receiver, index, holder, configuration)
-            : LookupIterator(receiver, name, holder, configuration);
-    it.name_ = name;
-    return it;
+    if (name->AsArrayIndex(&index)) {
+      LookupIterator it =
+          LookupIterator(isolate, receiver, index, holder, configuration);
+      it.name_ = name;
+      return it;
+    }
+    return LookupIterator(receiver, name, holder, configuration);
   }
 
   static LookupIterator PropertyOrElement(
       Isolate* isolate, Handle<Object> receiver, Handle<Object> key,
       bool* success, Configuration configuration = DEFAULT);
 
   void Restart() { RestartInternal(InterceptorState::kUninitialized); }
 
   Isolate* isolate() const { return isolate_; }
   State state() const { return state_; }
@@ skipping 174 matching lines @@
   Handle<JSReceiver> holder_;
   const Handle<JSReceiver> initial_holder_;
   uint32_t number_;
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_LOOKUP_H_