Add back references. Since "back references" is two words...

src/regexp-macro-assembler.h

 // Copyright 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 46 matching lines @@
   virtual void SetRegister(int register_index, int to) = 0;
   virtual void WriteCurrentPositionToRegister(int reg) = 0;
   virtual void ReadCurrentPositionFromRegister(int reg) = 0;
   virtual void WriteStackPointerToRegister(int reg) = 0;
   virtual void ReadStackPointerFromRegister(int reg) = 0;
   virtual void LoadCurrentCharacter(int cp_offset, Label* on_end_of_input) = 0;
   virtual void CheckCharacterLT(uc16 limit, Label* on_less) = 0;
   virtual void CheckCharacterGT(uc16 limit, Label* on_greater) = 0;
   virtual void CheckCharacter(uc16 c, Label* on_equal) = 0;
   virtual void CheckNotCharacter(uc16 c, Label* on_not_equal) = 0;
+  virtual void CheckNotBackReference(int start_reg, Label* on_no_match) = 0;
   // Check the current character for a match with a literal string.  If we
   // fail to match then goto the on_failure label.  End of input always
   // matches.  If the label is NULL then we should pop a backtrack address off
   // the stack abnd go to that.
   virtual void CheckCharacters(
       Vector<const uc16> str,
       int cp_offset,
       Label* on_failure) = 0;
   // Check the current input position against a register.  If the register is
   // equal to the current position then go to the label.  If the label is NULL
@@ skipping 78 matching lines @@
   ArraySlice<T> GetBuffer(int size, int align);
  private:
   const int byte_array_size_;
   Handle<ByteArray> current_byte_array_;
   int current_byte_array_free_offset_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGEXP_MACRO_ASSEMBLER_H_