Run test tearDowns and clean up temporary directories when a signal is caught.

lib/src/runner/browser/iframe_test.dart

 // Copyright (c) 2015, 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.
 
 library test.runner.browser.iframe_test;
 
 import '../../backend/live_test.dart';
 import '../../backend/live_test_controller.dart';
 import '../../backend/metadata.dart';
 import '../../backend/state.dart';
 import '../../backend/suite.dart';
 import '../../backend/test.dart';
 import '../../util/multi_channel.dart';
 import '../../util/remote_exception.dart';
 
 /// A test in a running iframe.
 class IframeTest implements Test {
   final String name;
   final Metadata metadata;
 
   /// The channel used to communicate with the test's [IframeListener].
   final MultiChannel _channel;
 
   IframeTest(this.name, this.metadata, this._channel);
 
   LiveTest load(Suite suite) {
     var controller;
+    var testChannel;
     controller = new LiveTestController(suite, this, () {
       controller.setState(const State(Status.running, Result.success));
 
-      var testChannel = _channel.virtualChannel();
+      testChannel = _channel.virtualChannel();
       _channel.sink.add({
         'command': 'run',
         'channel': testChannel.id
       });
 
       testChannel.stream.listen((message) {
         if (message['type'] == 'error') {
           var asyncError = RemoteException.deserialize(message['error']);
           controller.addError(asyncError.error, asyncError.stackTrace);
         } else if (message['type'] == 'state-change') {
           controller.setState(
               new State(
                   new Status.parse(message['status']),
                   new Result.parse(message['result'])));
         } else if (message['type'] == 'print') {
           controller.print(message['line']);
         } else {
           assert(message['type'] == 'complete');
           controller.completer.complete();
         }
       });
+    }, () {
+      // Ignore all future messages from the test and complete it immediately.
+      // We don't need to tell it to run its tear-down because there's nothing a
+      // browser test needs to clean up on the file system anyway.
+      testChannel.sink.close();
+      if (!controller.completer.isCompleted) controller.completer.complete();
     });
     return controller.liveTest;
   }
 }