RegExp replace with empty string optimization by Sandholm.

src/factory.h

 // Copyright 2006-2008 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 77 matching lines @@
   static Handle<String> NewStringFromAscii(
       Vector<const char> str,
       PretenureFlag pretenure = NOT_TENURED);
 
   // UTF8 strings are pretenured when used for regexp literal patterns and
   // flags in the parser.
   static Handle<String> NewStringFromUtf8(
       Vector<const char> str,
       PretenureFlag pretenure = NOT_TENURED);
 
-  static Handle<String> NewStringFromTwoByte(Vector<const uc16> str,
+  static Handle<String> NewStringFromTwoByte(
+      Vector<const uc16> str,
       PretenureFlag pretenure = NOT_TENURED);
 
-  // Allocates and partially initializes a TwoByte String. The characters of
-  // the string are uninitialized. Currently used in regexp code only, where
-  // they are pretenured.
+  // Allocates and partially initializes an ASCII or TwoByte String. The
+  // characters of the string are uninitialized. Currently used in regexp code
+  // only, where they are pretenured.
+  static Handle<String> NewRawAsciiString(
+      int length,
+      PretenureFlag pretenure = NOT_TENURED);
   static Handle<String> NewRawTwoByteString(
       int length,
       PretenureFlag pretenure = NOT_TENURED);
 
   // Create a new cons string object which consists of a pair of strings.
   static Handle<String> NewConsString(Handle<String> first,
                                       Handle<String> second);
 
   // Create a new string object which holds a substring of a string.
   static Handle<String> NewSubString(Handle<String> str,
@@ skipping 284 matching lines @@
   // Update the map cache in the global context with (keys, map)
   static Handle<MapCache> AddToMapCache(Handle<Context> context,
                                         Handle<FixedArray> keys,
                                         Handle<Map> map);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_FACTORY_H_