[runtime] Add fast path to update LookupIterator in simple cases

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 269 matching lines @@
   inline InterceptorInfo* GetInterceptor(JSObject* holder) const {
     if (IsElement()) return holder->GetIndexedInterceptor();
     return holder->GetNamedInterceptor();
   }
 
   bool check_hidden() const { return (configuration_ & kHidden) != 0; }
   bool check_interceptor() const {
     return (configuration_ & kInterceptor) != 0;
   }
   int descriptor_number() const {
+    DCHECK(!IsElement());
     DCHECK(has_property_);
     DCHECK(!holder_map_->is_dictionary_map());
     return number_;
   }
   int dictionary_entry() const {
+    DCHECK(!IsElement());
     DCHECK(has_property_);
     DCHECK(holder_map_->is_dictionary_map());
     return number_;
   }
 
   static Configuration ComputeConfiguration(
       Configuration configuration, Handle<Name> name) {
     if (name->IsPrivate()) {
       return static_cast<Configuration>(configuration &
                                         HIDDEN_SKIP_INTERCEPTOR);
@@ skipping 29 matching lines @@
   Handle<Map> holder_map_;
   const Handle<JSReceiver> initial_holder_;
   uint32_t number_;
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_LOOKUP_H_