Make RegExp constructor non-const.

utils/tests/pub/test_pub.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.
 
 /**
  * Test infrastructure for testing pub. Unlike typical unit tests, most pub
  * tests are integration tests that stage some stuff on the file system, run
  * pub, and then validate the results. This library provides an API to build
  * tests like that.
  */
@@ skipping 391 matching lines @@
     return result;
   });
 }
 
 /// Return the name for the package described by [description] and from
 /// [sourceName].
 String _packageName(String sourceName, description) {
   switch (sourceName) {
   case "git":
     var url = description is String ? description : description['url'];
-    return basename(url.replaceFirst(const RegExp(r"(\.git)?/?$"), ""));
+    return basename(url.replaceFirst(new RegExp(r"(\.git)?/?$"), ""));
   case "hosted":
     if (description is String) return description;
     return description['name'];
   case "sdk":
     return description;
   default:
     return description;
   }
 }
 
@@ skipping 801 matching lines @@
 }
 
 /**
  * Schedules a callback to be called after Pub is run with [runPub], even if it
  * fails.
  */
 void _scheduleCleanup(_ScheduledEvent event) {
   if (_scheduledCleanup == null) _scheduledCleanup = [];
   _scheduledCleanup.add(event);
 }