Handle overwriting valueOf on String objects correctly when adding...

src/x64/codegen-x64.h

Index: src/x64/codegen-x64.h
===================================================================
--- src/x64/codegen-x64.h	(revision 5232)
+++ src/x64/codegen-x64.h	(working copy)
@@ -347,6 +347,10 @@
   // expected arguments. Otherwise return -1.
   static int InlineRuntimeCallArgumentsCount(Handle<String> name);
 
+  static Operand ContextOperand(Register context, int index) {
+    return Operand(context, Context::SlotOffset(index));
+  }
+
  private:
   // Construction/Destruction
   explicit CodeGenerator(MacroAssembler* masm);
@@ -406,10 +410,6 @@
   void LoadReference(Reference* ref);
   void UnloadReference(Reference* ref);
 
-  static Operand ContextOperand(Register context, int index) {
-    return Operand(context, Context::SlotOffset(index));
-  }
-
   Operand SlotOperand(Slot* slot, Register tmp);
 
   Operand ContextSlotOperandCheckExtensions(Slot* slot,
@@ -611,6 +611,8 @@
   void GenerateIsSpecObject(ZoneList<Expression*>* args);
   void GenerateIsFunction(ZoneList<Expression*>* args);
   void GenerateIsUndetectableObject(ZoneList<Expression*>* args);
+  void GenerateIsStringWrapperSafeForDefaultValueOf(
+      ZoneList<Expression*>* args);
 
   // Support for construct call checks.
   void GenerateIsConstructCall(ZoneList<Expression*>* args);