Fastpath some spread-call desugaring.

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/globals.h"
 #include "src/isolate.h"
@@ skipping 240 matching lines @@
     return handle(result, isolate_);
   }
   Handle<InterceptorInfo> GetInterceptorForFailedAccessCheck() const;
   Handle<Object> GetDataValue() const;
   void WriteDataValue(Handle<Object> value);
   inline void UpdateProtector() {
     if (IsElement()) return;
     if (*name_ == heap()->is_concat_spreadable_symbol() ||
         *name_ == heap()->constructor_string() ||
         *name_ == heap()->species_symbol() ||
-        *name_ == heap()->has_instance_symbol()) {
+        *name_ == heap()->has_instance_symbol() ||
+        *name_ == heap()->iterator_symbol()) {
       InternalUpdateProtector();
     }
   }
 
   // Lookup a 'cached' private property for an accessor.
   // If not found returns false and leaves the LookupIterator unmodified.
   bool TryLookupCachedProperty();
   bool LookupCachedProperty();
 
  private:
@@ skipping 88 matching lines @@
   const Handle<JSReceiver> initial_holder_;
   const uint32_t index_;
   uint32_t number_;
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_LOOKUP_H_