Reduce flakiness of browser tests.

tools/testing/dart/test_suite.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.
 
 #library("test_suite");
 
 #import("dart:io");
 #import("status_file_parser.dart");
 #import("test_runner.dart");
 #import("multitest.dart");
@@ skipping 423 matching lines @@
       if (new Platform().operatingSystem() == 'windows') {
         // Firefox on Windows does not like absolute file path names that start
         // with 'C:' adding 'file:///' solves the problem.
         filePrefix = 'file:///';
       }
       htmlTest.writeStringSync(GetHtmlContents(
           filename,
           '$filePrefix$dartDir/client/testing/unittest/test_controller.js',
           scriptType,
           filePrefix + scriptPath));
+      htmlTest.flushSync();
       htmlTest.closeSync();
 
       List<String> compilerArgs = TestUtils.standardOptions(configuration);
       String compilerExecutable = TestUtils.compilerPath(configuration);
       switch (component) {
         case 'chromium':
           compilerArgs.addAll(['--work', tempDir.path]);
           compilerArgs.addAll(vmOptions);
           compilerArgs.add('--ignore-unrecognized-flags');
           // TODO(zundel): remove assumption of generated code from dartc
@@ skipping 602 matching lines @@
  * $noCrash tests are expected to be flaky but not crash
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
 """;
     print(report);
    }
 }