Start two http servers for every configuration

tools/testing/dart/test_runner.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.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 1582 matching lines @@
         _tests.add(test);
         new Timer(100, (_) => _tryRunTest());  // Don't lose a process.
         return;
       }
       // Before running any commands, we print out all commands if '--verbose'
       // was specified.
       if (_verbose && test.commandOutputs.length == 0) {
         int i = 1;
         if (test is BrowserTestCase) {
           // Additional command for rerunning the steps locally after the fact.
-          print('$i. ${TestUtils.dartTestExecutable.toNativePath()} '
-                '${TestUtils.dartDir().toNativePath()}/tools/testing/dart/'
-                'http_server.dart -m ${test.configuration["mode"]} '
-                '-a ${test.configuration["arch"]} '
-                '-p ${http_server.TestingServerRunner.serverList[0].port} '
-                '-c ${http_server.TestingServerRunner.serverList[1].port} '
-                '--package-root='
-                '${http_server.TestingServerRunner.packageRootDir}');
+          var command =
+            test.configuration["_servers_"].httpServerCommandline();
+          print('$i. $command');
           i++;
         }
         for (Command command in test.commands) {
           print('$i. ${command.commandLine}');
           i++;
         }
       }
 
       var isLastCommand =
           ((test.commands.length-1) == test.commandOutputs.length);
@@ skipping 132 matching lines @@
           completer.complete(testCase);
         }
       });
     }
     runCommand();
 
     return completer.future;
   }
 }