Fix hanging test script batch runners.

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 1946 matching lines @@
         doStartTest(command, timeout);
       });
     } else if (!sameRunnerType) {
       // Restart this runner with the right executable for this test if needed.
       _processExitHandler = (_) {
         _startProcess(() {
           doStartTest(command, timeout);
         });
       };
       _process.kill();
+      _stdoutSubscription.cancel();
+      _stderrSubscription.cancel();
     } else {
       doStartTest(command, timeout);
     }
     return _completer.future;
   }
 
   Future terminate() {
     if (_process == null) return new Future.value(true);
     Completer terminateCompleter = new Completer();
-    Timer killTimer;
     _processExitHandler = (_) {
-      if (killTimer != null) killTimer.cancel();
       terminateCompleter.complete(true);
     };
     _process.kill();
+    _stdoutSubscription.cancel();
+    _stderrSubscription.cancel();
 
     return terminateCompleter.future;
   }
 
   void doStartTest(Command command, int timeout) {
     _startTime = new DateTime.now();
     _testStdout = new OutputLog();
     _testStderr = new OutputLog();
     _status = null;
     _stdoutCompleter = new Completer();
@@ skipping 948 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }