Revert "Use browsers JSON.parse for parsing JSON (#3)"

tests/corelib/json_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library json_test;
 
 import "dart:json";
 
 bool badFormat(e) => e is FormatException;
 
@@ skipping 79 matching lines @@
         }
       }
     }
   }
   // Doubles overflow to Infinity.
   testJson("1e+400", double.INFINITY);
   // (Integers do not, but we don't have those on dart2js).
 
   // Integer part cannot be omitted:
   testError(integers: "");
-
-  // Test for "Initial zero only allowed for zero integer part" moved to
-  // json_leading_zeros_test.dart because IE's JSON.parse accepts additional
-  // initial zeros.
-
+  // Initial zero only allowed for zero integer part.
+  testError(integers: ["00", "01"]);
   // Only minus allowed as sign.
   testError(signs: "+");
   // Requires digits after decimal point.
   testError(fractions: ".");
   // Requires exponent digts, and only digits.
   testError(exponents: ["e", "e+", "e-", "e.0"]);
 
   // No whitespace inside numbers.
   testThrows("- 2.2e+2");
   testThrows("-2 .2e+2");
@@ skipping 130 matching lines @@
 }
 
 main() {
   testNumbers();
   testStrings();
   testWords();
   testObjects();
   testArrays();
   testWhitespace();
 }