Using KeyedStoreIC_Generic_Strict must prevent polymorphic case.

src/type-info.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 104 matching lines @@
 }
 
 
 bool TypeFeedbackOracle::StoreIsMegamorphicWithTypeInfo(Expression* expr) {
   Handle<Object> map_or_code(GetInfo(expr->id()));
   if (map_or_code->IsCode()) {
     Handle<Code> code = Handle<Code>::cast(map_or_code);
     Builtins* builtins = Isolate::Current()->builtins();
     return code->is_keyed_store_stub() &&
         *code != builtins->builtin(Builtins::kKeyedStoreIC_Generic) &&
+        *code != builtins->builtin(Builtins::kKeyedStoreIC_Generic_Strict) &&
         code->ic_state() == MEGAMORPHIC;
   }
   return false;
 }
 
 
 bool TypeFeedbackOracle::CallIsMonomorphic(Call* expr) {
   Handle<Object> value = GetInfo(expr->id());
   return value->IsMap() || value->IsSmi();
 }
@@ skipping 402 matching lines @@
   USE(maybe_result);
 #ifdef DEBUG
   Object* result = NULL;
   // Dictionary has been allocated with sufficient size for all elements.
   ASSERT(maybe_result->ToObject(&result));
   ASSERT(*dictionary_ == result);
 #endif
 }
 
 } }  // namespace v8::internal