Add a public API for using an empty sring.

include/v8.h

 // Copyright 2007-2008 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 718 matching lines @@
    * copying begins.
    * \param length The number of bytes to copy from the string.
    * \return The number of characters copied to the buffer
    * excluding the NULL terminator.
    */
   int Write(uint16_t* buffer, int start = 0, int length = -1) const;  // UTF-16
   int WriteAscii(char* buffer, int start = 0, int length = -1) const;  // ASCII
   int WriteUtf8(char* buffer, int length = -1) const; // UTF-8
 
   /**
+   * A zero length string.
+   */
+  static v8::Local<v8::String> Empty();
+
+  /**
    * Returns true if the string is external
    */
   bool IsExternal() const;
 
   /**
    * Returns true if the string is both external and ascii
    */
   bool IsExternalAscii() const;
   /**
    * An ExternalStringResource is a wrapper around a two-byte string
@@ skipping 1746 matching lines @@
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef V8EXPORT_INLINE
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_