[es6] don't "replace" Object.prototype.toString for --harmony-tostring

src/runtime/runtime.h

 // Copyright 2012 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_RUNTIME_RUNTIME_H_
 #define V8_RUNTIME_RUNTIME_H_
 
 #include "src/allocation.h"
 #include "src/objects.h"
 #include "src/zone.h"
@@ skipping 272 matching lines @@
   F(AllocateInTargetSpace, 2, 1)          \
   F(CollectStackTrace, 2, 1)              \
   F(RenderCallSite, 0, 1)                 \
   F(GetFromCacheRT, 2, 1)                 \
   F(MessageGetStartPosition, 1, 1)        \
   F(MessageGetScript, 1, 1)               \
   F(IS_VAR, 1, 1)                         \
   F(GetFromCache, 2, 1)                   \
   F(IncrementStatsCounter, 1, 1)          \
   F(Likely, 1, 1)                         \
-  F(Unlikely, 1, 1)
+  F(Unlikely, 1, 1)                       \
+  F(HarmonyToString, 0, 1)
 
 
 #define FOR_EACH_INTRINSIC_JSON(F) \
   F(QuoteJSONString, 1, 1)         \
   F(BasicJSONStringify, 1, 1)      \
   F(ParseJson, 1, 1)
 
 
 #define FOR_EACH_INTRINSIC_LITERALS(F)   \
   F(CreateObjectLiteral, 4, 1)           \
@@ skipping 552 matching lines @@
 
 class DeclareGlobalsEvalFlag : public BitField<bool, 0, 1> {};
 class DeclareGlobalsNativeFlag : public BitField<bool, 1, 1> {};
 STATIC_ASSERT(LANGUAGE_END == 3);
 class DeclareGlobalsLanguageMode : public BitField<LanguageMode, 2, 2> {};
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_RUNTIME_RUNTIME_H_