Tag stubs that rely on instance types as MEGAMORPHIC.

src/builtins.h

 // 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 127 matching lines @@
                                     Code::kNoExtraICState)              \
   V(LoadIC_Getter_ForDeopt,         LOAD_IC, MONOMORPHIC,               \
                                     Code::kNoExtraICState)              \
                                                                         \
   V(KeyedLoadIC_Initialize,         KEYED_LOAD_IC, UNINITIALIZED,       \
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_PreMonomorphic,     KEYED_LOAD_IC, PREMONOMORPHIC,      \
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_Generic,            KEYED_LOAD_IC, GENERIC,             \
                                     Code::kNoExtraICState)              \
-  V(KeyedLoadIC_String,             KEYED_LOAD_IC, MONOMORPHIC,         \
+  V(KeyedLoadIC_String,             KEYED_LOAD_IC, MEGAMORPHIC,         \
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_IndexedInterceptor, KEYED_LOAD_IC, MONOMORPHIC,         \
                                     Code::kNoExtraICState)              \
   V(KeyedLoadIC_NonStrictArguments, KEYED_LOAD_IC, MONOMORPHIC,         \
                                     Code::kNoExtraICState)              \
                                                                         \
   V(StoreIC_Initialize,             STORE_IC, UNINITIALIZED,            \
                                     Code::kNoExtraICState)              \
   V(StoreIC_Normal,                 STORE_IC, MONOMORPHIC,              \
                                     Code::kNoExtraICState)              \
@@ skipping 244 matching lines @@
 
   friend class BuiltinFunctionTable;
   friend class Isolate;
 
   DISALLOW_COPY_AND_ASSIGN(Builtins);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_BUILTINS_H_