make empty string returnable by ReturnValue

include/v8.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 2827 matching lines @@
   template <typename S> V8_INLINE(void Set(const Persistent<S>& handle));
   template <typename S> V8_INLINE(void Set(const Handle<S> handle));
   // Fast primitive setters
   V8_INLINE(void Set(bool value));
   V8_INLINE(void Set(double i));
   V8_INLINE(void Set(int32_t i));
   V8_INLINE(void Set(uint32_t i));
   // Fast JS primitive setters
   V8_INLINE(void SetNull());
   V8_INLINE(void SetUndefined());
+  V8_INLINE(void SetEmptyString());
   // Convenience getter for Isolate
   V8_INLINE(Isolate* GetIsolate());
 
  private:
   template<class F> friend class ReturnValue;
   template<class F> friend class FunctionCallbackInfo;
   template<class F> friend class PropertyCallbackInfo;
   V8_INLINE(internal::Object* GetDefaultValue());
   V8_INLINE(explicit ReturnValue(internal::Object** slot));
   internal::Object** value_;
@@ skipping 2865 matching lines @@
   *value_ = *I::GetRoot(GetIsolate(), I::kNullValueRootIndex);
 }
 
 template<typename T>
 void ReturnValue<T>::SetUndefined() {
   typedef internal::Internals I;
   *value_ = *I::GetRoot(GetIsolate(), I::kUndefinedValueRootIndex);
 }
 
 template<typename T>
+void ReturnValue<T>::SetEmptyString() {
+  typedef internal::Internals I;
+  *value_ = *I::GetRoot(GetIsolate(), I::kEmptyStringRootIndex);
+}
+
+template<typename T>
 Isolate* ReturnValue<T>::GetIsolate() {
   // Isolate is always the pointer below the default value on the stack.
   return *reinterpret_cast<Isolate**>(&value_[-2]);
 }
 
 template<typename T>
 internal::Object* ReturnValue<T>::GetDefaultValue() {
   // Default value is always the pointer below value_ on the stack.
   return value_[-1];
 }
@@ skipping 584 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_