Reduce temporarily flakiness rate of dart2js-drt by re-running until they have been fixed

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 2964 matching lines @@
       }
     }
 
     // We currently rerun dartium tests, see issue 14074.
     if (command is BrowserTestCommand &&
         command.retry &&
         command.browser == 'dartium') {
       return true;
     }
 
+    // As long as we use a legacy version of our custom content_shell (which
+    // became quite flaky after chrome-50 roll) we'll re-run tests on it.
+    // The plan is to use chrome's content_shell instead of our own.
+    // See http://dartbug.com/29655 .
+    if (command is ContentShellCommand) {
+      return true;
+    }
+
     if (io.Platform.operatingSystem == 'linux') {
       decodeOutput();
       // No matter which command we ran: If we get failures due to the
       // "xvfb-run" issue 7564, try re-running the test.
       bool containsFailureMsg(String line) {
         return line.contains(MESSAGE_CANNOT_OPEN_DISPLAY) ||
             line.contains(MESSAGE_FAILED_TO_RUN_COMMAND);
       }
 
       if (stdout.any(containsFailureMsg) || stderr.any(containsFailureMsg)) {
@@ skipping 296 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }