fix special index parsing

src/conversions.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CONVERSIONS_H_
 #define V8_CONVERSIONS_H_
 
 #include <limits>
 
 #include "src/base/logging.h"
@@ skipping 219 matching lines @@
 // Converts a number into size_t.
 inline size_t NumberToSize(Isolate* isolate,
                            Object* number) {
   size_t result = 0;
   bool is_valid = TryNumberToSize(isolate, number, &result);
   CHECK(is_valid);
   return result;
 }
 
 
-bool IsNonArrayIndexInteger(String* string);
+// returns DoubleToString(StringToDouble(string)) == string
+bool IsSpecialIndex(UnicodeCache* unicode_cache, String* string);
 } }  // namespace v8::internal
 
 #endif  // V8_CONVERSIONS_H_