[es6] Correct parsing of regular expression literal flags.

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 340 matching lines @@
 
 test(function() {
   Reflect.construct(function() {}, 1);
 }, "Reflect.construct: Arguments list has wrong type", TypeError);
 
 
 // === SyntaxError ===
 
 // kInvalidRegExpFlags
 test(function() {
-  /a/x.test("a");
-}, "Invalid flags supplied to RegExp constructor 'x'", SyntaxError);
+  eval("/a/x.test(\"a\");");
+}, "Invalid regular expression flags", SyntaxError);
 
 // kMalformedRegExp
 test(function() {
   /(/.test("a");
 }, "Invalid regular expression: /(/: Unterminated group", SyntaxError);
 
 // kParenthesisInArgString
 test(function() {
   new Function(")", "");
 }, "Function arg string contains parenthesis", SyntaxError);
@@ skipping 90 matching lines @@
   Number(1).toString(100);
 }, "toString() radix argument must be between 2 and 36", RangeError);
 
 
 // === URIError ===
 
 // kURIMalformed
 test(function() {
   decodeURI("%%");
 }, "URI malformed", URIError);