Make RegExp's constructor non-const.

pkg/unittest/lib/src/config.dart

 // Copyright (c) 2011, 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.
 
 part of unittest;
 
 /**
  * Hooks to configure the unittest library for different platforms. This class
  * implements the API in a platform-independent way. Tests that want to take
  * advantage of the platform can create a subclass and override methods from
@@ skipping 115 matching lines @@
 
     if (success) {
       _postMessage('unittest-suite-success');
     } else {
       throw new Exception('Some tests failed.');
     }
   }
 
   String _indent(String str) {
     // TODO(nweiz): Use this simpler code once issue 2980 is fixed.
-    // return str.replaceAll(const RegExp("^", multiLine: true), "  ");
+    // return str.replaceAll(new RegExp("^", multiLine: true), "  ");
 
     return Strings.join(str.split("\n").map((line) => "  $line"), "\n");
   }
 
   /** Handle errors that happen outside the tests. */
   // TODO(vsm): figure out how to expose the stack trace here
   // Currently e.message works in dartium, but not in dartc.
   handleExternalError(e, String message) =>
       _reportTestError('$message\nCaught $e', '');
 
   _postMessage(String message) {
     // In dart2js browser tests, the JavaScript-based test controller
     // intercepts calls to print and listens for "secret" messages.
     print(message);
   }
 }