When only listing and not running tests, don't start the http server.

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 109 matching lines @@
       if (selectors.containsKey(name)) {
         queue.addTestSuite(
             new StandardTestSuite.forDirectory(conf, testSuiteDir));
       }
     }
   }
 
   // Start global http server that serves the entire dart repo.
   // The http server is available on localhost:9876 for any
   // test that needs to load resources from the repo over http.
-  startHttpServer('127.0.0.1', 9876);
+  if (!listTests) startHttpServer('127.0.0.1', 9876);
 
   // Start process queue.
   new ProcessQueue(
       maxProcesses,
       progressIndicator,
       startTime,
       printTiming,
       enqueueConfiguration,
-      () => terminateHttpServer(),
+      () {
+        if (!listTests) terminateHttpServer();
+      },
       verbose,
       listTests);
 }