Upgrade Symbol implementation to match current ES6 behavior.

src/runtime.h

 // Copyright 2012 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 297 matching lines @@
   \
   /* ES5 */ \
   F(ObjectFreeze, 1, 1) \
   \
   /* Harmony modules */ \
   F(IsJSModule, 1, 1) \
   \
   /* Harmony symbols */ \
   F(CreateSymbol, 1, 1) \
   F(CreatePrivateSymbol, 1, 1) \
-  F(SymbolName, 1, 1) \
+  F(SymbolDescription, 1, 1) \
   F(SymbolIsPrivate, 1, 1) \
+  F(SymbolGetSymbolData, 1, 1) \
+  F(SymbolSetSymbolData, 2, 1) \
   \
   /* Harmony proxies */ \
   F(CreateJSProxy, 2, 1) \
   F(CreateJSFunctionProxy, 4, 1) \
   F(IsJSProxy, 1, 1) \
   F(IsJSFunctionProxy, 1, 1) \
   F(GetHandler, 1, 1) \
   F(GetCallTrap, 1, 1) \
   F(GetConstructTrap, 1, 1) \
   F(Fix, 1, 1) \
@@ skipping 533 matching lines @@
 class AllocateDoubleAlignFlag:    public BitField<bool,            0, 1> {};
 class AllocateTargetSpace:        public BitField<AllocationSpace, 1, 3> {};
 
 class DeclareGlobalsEvalFlag:     public BitField<bool,         0, 1> {};
 class DeclareGlobalsNativeFlag:   public BitField<bool,         1, 1> {};
 class DeclareGlobalsLanguageMode: public BitField<LanguageMode, 2, 2> {};
 
 } }  // namespace v8::internal
 
 #endif  // V8_RUNTIME_H_