Support re-running tests while debugging.

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/group.dart';
 import '../../backend/live_test.dart';
 import '../../backend/live_test_controller.dart';
 import '../../backend/metadata.dart';
 import '../../backend/operating_system.dart';
 import '../../backend/state.dart';
 import '../../backend/suite.dart';
 import '../../backend/test.dart';
 import '../../backend/test_platform.dart';
+import '../../utils.dart';
 import '../../util/multi_channel.dart';
 import '../../util/remote_exception.dart';
 import '../../util/stack_trace_mapper.dart';
 
 /// A test in a running iframe.
 class IframeTest extends Test {
   final String name;
   final Metadata metadata;
 
   /// The mapper used to map stack traces for errors coming from this test, or
@@ skipping 30 matching lines @@
           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();
         }
+      }, onDone: () {
+        // When the test channel closes—presumably becuase the browser
+        // closed—mark the test as complete no matter what.
+        if (controller.completer.isCompleted) return;
+        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();
+      // If the test has finished running, just disconnect the channel.
+      if (controller.completer.isCompleted) {
+        testChannel.sink.close();
+        return;
+      }
+
+      invoke(() async {
+        // If the test is still running, send it a message telling it to shut
+        // down ASAP. This causes the [Invoker] to eagerly throw exceptions
+        // whenever the test touches it.
+        testChannel.sink.add({'command': 'close'});
+        await controller.completer.future;
+        testChannel.sink.close();
+      });
     }, groups: groups);
     return controller.liveTest;
   }
 
   Test forPlatform(TestPlatform platform, {OperatingSystem os}) {
     if (!metadata.testOn.evaluate(platform, os: os)) return null;
     return new IframeTest(
         name, metadata.forPlatform(platform, os: os), _channel,
         mapper: _mapper);
   }
 }