Gracefully handle tests that print.

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 unittest.runner.browser.iframe_test;
 
 import '../../backend/live_test.dart';
 import '../../backend/live_test_controller.dart';
 import '../../backend/metadata.dart';
 import '../../backend/state.dart';
@@ skipping 25 matching lines @@
 
       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();
         }
       });
     });
     return controller.liveTest;
   }
 }