[runtime] Don't cache the holder_map_ in the LookupIterator, it's faster.

src/objects.cc

 // Copyright 2015 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.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 4414 matching lines @@
                       !it->isolate()->IsInternallyUsedPropertyName(it->name()));
   MaybeHandle<Object> maybe_old;
   if (is_observed) maybe_old = it->GetDataValue();
 
   Handle<Object> to_assign = value;
   // Convert the incoming value to a number for storing into typed arrays.
   if (it->IsElement() && receiver->HasFixedTypedArrayElements()) {
     if (!value->IsNumber() && !value->IsUndefined()) {
       ASSIGN_RETURN_ON_EXCEPTION_VALUE(
           it->isolate(), to_assign, Object::ToNumber(value), Nothing<bool>());
-      // ToNumber above might modify the receiver, causing the cached
-      // holder_map to mismatch the actual holder->map() after this point.
-      // Reload the map to be in consistent state. Other cached state cannot
-      // have been invalidated since typed array elements cannot be reconfigured
-      // in any way.
-      it->ReloadHolderMap();
-
       // We have to recheck the length. However, it can only change if the
       // underlying buffer was neutered, so just check that.
       if (Handle<JSArrayBufferView>::cast(receiver)->WasNeutered()) {
         return Just(true);
         // TODO(neis): According to the spec, this should throw a TypeError.
       }
     }
   }
 
   // Possibly migrate to the most up-to-date map that will be able to store
@@ skipping 15468 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8