[json parser] add position to error message.

test/mjsunit/messages.js

 // Copyright 2015 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.
 
 // Flags: --stack-size=100 --harmony --harmony-reflect --harmony-regexps
 // Flags: --harmony-simd --strong-mode
 
 function test(f, expected, type) {
   try {
     f();
@@ skipping 327 matching lines @@
    "and a value or writable attribute, #<Object>", TypeError);
 
 
 // === SyntaxError ===
 
 // kInvalidRegExpFlags
 test(function() {
   eval("/a/x.test(\"a\");");
 }, "Invalid regular expression flags", SyntaxError);
 
+//kJsonParseUnexpectedEOS
+test(function() {
+  JSON.parse("{")
+}, "Unexpected end of JSON input", SyntaxError);
+
+// kJsonParseUnexpectedTokenAt
+test(function() {
+  JSON.parse("/")
+}, "Unexpected token / in JSON at position 0", SyntaxError);
+
+// kJsonParseUnexpectedTokenNumberAt
+test(function() {
+  JSON.parse("{ 1")
+}, "Unexpected number in JSON at position 2", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringAt
+test(function() {
+  JSON.parse('"""')
+}, "Unexpected string in JSON at position 2", SyntaxError);
+
 // kMalformedRegExp
 test(function() {
   /(/.test("a");
 }, "Invalid regular expression: /(/: Unterminated group", SyntaxError);
 
 // kParenthesisInArgString
 test(function() {
   new Function(")", "");
 }, "Function arg string contains parenthesis", SyntaxError);
 
-// kUnexpectedEOS
-test(function() {
-  JSON.parse("{")
-}, "Unexpected end of input", SyntaxError);
-
-// kUnexpectedToken
-test(function() {
-  JSON.parse("/")
-}, "Unexpected token /", SyntaxError);
-
-// kUnexpectedTokenNumber
-test(function() {
-  JSON.parse("{ 1")
-}, "Unexpected number", SyntaxError);
-
-// kUnexpectedTokenString
-test(function() {
-  JSON.parse('"""')
-}, "Unexpected string", SyntaxError);
-
-
 // === ReferenceError ===
 
 // kNotDefined
 test(function() {
   "use strict";
   o;
 }, "o is not defined", ReferenceError);
 
 // === RangeError ===
 
@@ skipping 58 matching lines @@
   Number(1).toString(100);
 }, "toString() radix argument must be between 2 and 36", RangeError);
 
 
 // === URIError ===
 
 // kURIMalformed
 test(function() {
   decodeURI("%%");
 }, "URI malformed", URIError);