Utilize all cores on IE bots

tools/test.dart

 #!/usr/bin/env 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.
 
 /**
  * This file is the entrypoint of the dart test suite.  This suite is used
  * to test:
  *
  *     1. the dart vm
@@ skipping 110 matching lines @@
       TestingServerRunner.startHttpServer('127.0.0.1');
       // We start two servers so that we can test cross-domain tests.
       TestingServerRunner.startHttpServer('127.0.0.1',
           allowedPort: TestingServerRunner.serverList[0].port);
     }
   }
 
   var testSuites = new List<TestSuite>();
   var maxBrowserProcesses = maxProcesses;
   for (var conf in configurations) {
-    // We can't run multiple IE processes in parallel.
+    // There should not be more than one InternetExplorerDriver instance
+    // running at a time. For details, see
+    // http://code.google.com/p/selenium/wiki/InternetExplorerDriver.
     if (conf['runtime'].startsWith('ie')) {
       maxBrowserProcesses = 1;
     }
     TestingServerRunner.setPackageRootDir(conf);
     for (String key in selectors.keys) {
       if (key == 'co19') {
         testSuites.add(new Co19TestSuite(conf));
       } else if (conf['runtime'] == 'vm' && key == 'vm') {
         // vm tests contain both cc tests (added here) and dart tests (added in
         // [TEST_SUITE_DIRECTORIES]).
@@ skipping 23 matching lines @@
   new ProcessQueue(maxProcesses,
                    maxBrowserProcesses,
                    progressIndicator,
                    startTime,
                    printTiming,
                    testSuites,
                    allTestsFinished,
                    verbose,
                    listTests);
 }