Expose a hint which communicates that string might be written many times.

include/v8.h

 // Copyright 2007-2009 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 841 matching lines @@
    * Only null-terminates if there is enough space in the buffer.
    *
    * \param buffer The buffer into which the string will be copied.
    * \param start The starting position within the string at which
    * copying begins.
    * \param length The number of bytes to copy from the string.
    * \param nchars_ref The number of characters written, can be NULL.
    * \return The number of bytes 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
+  enum WriteHints {
+    NO_HINTS = 0,
+    HINT_MANY_WRITES_EXPECTED = 1
+  };
+
+  int Write(uint16_t* buffer,
+            int start = 0,
+            int length = -1,
+            WriteHints hints = NO_HINTS) const;  // UTF-16
+  int WriteAscii(char* buffer,
+                 int start = 0,
+                 int length = -1,
+                 WriteHints hints = NO_HINTS) const;  // ASCII
   int WriteUtf8(char* buffer,
                 int length = -1,
-                int* nchars_ref = NULL) const; // UTF-8
-
-  /**
-   * Flatten internal memory. Operations on the string tend to run faster
-   * after flattening especially if the string is a concatenation of many
-   * others.
-   */
-  void Flatten();
+                int* nchars_ref = NULL,
+                WriteHints hints = NO_HINTS) const; // UTF-8
 
   /**
    * A zero length string.
    */
   static v8::Local<v8::String> Empty();
 
   /**
    * Returns true if the string is external
    */
   bool IsExternal() const;
@@ skipping 2515 matching lines @@
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef V8EXPORT_INLINE
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_