Make RegExp's constructor non-const.

tests/compiler/dart2js/boolified_operator_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 boolified_operator_test;
 import 'compiler_helper.dart';
 
 const String TEST_EQUAL = r"""
 foo(param0, param1) {
   if (param0 == param1) return 0;
@@ skipping 29 matching lines @@
 """;
 
 const String TEST_GREATER_EQUAL = r"""
 foo(param0, param1) {
   if (param0 >= param1) return 0;
   return 1;
 }
 """;
 
 main() {
-  RegExp regexp = const RegExp('=== true');
+  RegExp regexp = new RegExp('=== true');
 
   String generated = compile(TEST_EQUAL, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('eqB'));
 
   generated = compile(TEST_EQUAL_NULL, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('== null'));
 
   generated = compile(TEST_LESS, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('ltB'));
 
   generated = compile(TEST_LESS_EQUAL, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('leB'));
   
   generated = compile(TEST_GREATER, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('gtB'));
   
   generated = compile(TEST_GREATER_EQUAL, entry: 'foo');
   Expect.isFalse(generated.contains('=== true'));
   Expect.isTrue(generated.contains('geB'));
 }