Don't pass the "at start" parameter to native RegExp...

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 200 matching lines @@
 
   static Address word_character_map_address() {
     return &word_character_map[0];
   }
 
   static Result Execute(Code* code,
                         String* input,
                         int start_offset,
                         const byte* input_start,
                         const byte* input_end,
-                        int* output,
-                        bool at_start);
+                        int* output);
 };
 
 #endif  // V8_NATIVE_REGEXP
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGEXP_MACRO_ASSEMBLER_H_