[runtime] Add instance size check for CheckEquivalent().

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 <memory>
 #include <sstream>
@@ skipping 12278 matching lines @@
   }
   return true;
 }
 
 
 bool Map::EquivalentToForNormalization(Map* other,
                                        PropertyNormalizationMode mode) {
   int properties =
       mode == CLEAR_INOBJECT_PROPERTIES ? 0 : other->GetInObjectProperties();
   return CheckEquivalent(this, other) && bit_field2() == other->bit_field2() &&
-         GetInObjectProperties() == properties;
+         GetInObjectProperties() == properties &&
+         JSObject::GetInternalFieldCount(this) ==
+             JSObject::GetInternalFieldCount(other);
 }
 
 
 bool JSFunction::Inlines(SharedFunctionInfo* candidate) {
   DisallowHeapAllocation no_gc;
   if (shared() == candidate) return true;
   if (code()->kind() != Code::OPTIMIZED_FUNCTION) return false;
   DeoptimizationInputData* const data =
       DeoptimizationInputData::cast(code()->deoptimization_data());
   if (data->length() == 0) return false;
@@ skipping 8124 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8