Add suppression to test.dart for flaky content_shell crashes

tools/testing/dart/test_configurations.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_configurations;
 
 import "dart:async";
 import 'dart:io';
 import "dart:math" as math;
 
@@ skipping 38 matching lines @@
   new Path('utils/tests/css'),
   new Path('utils/tests/peg'),
 ];
 
 Future testConfigurations(List<Map> configurations) async {
   var startTime = new DateTime.now();
   // Extract global options from first configuration.
   var firstConf = configurations[0];
   var maxProcesses = firstConf['tasks'];
   var progressIndicator = firstConf['progress'];
-  // TODO(kustermann): Remove this option once the buildbots don't use it
-  // anymore.
-  var failureSummary = firstConf['failure-summary'];
   BuildbotProgressIndicator.stepName = firstConf['step_name'];
   var verbose = firstConf['verbose'];
   var printTiming = firstConf['time'];
   var listTests = firstConf['list'];
 
   var reportInJson = firstConf['report_in_json'];
 
   var recordingPath = firstConf['record_to_file'];
   var recordingOutputPath = firstConf['replay_from_file'];
 
@@ skipping 233 matching lines @@
       maxBrowserProcesses,
       startTime,
       testSuites,
       eventListener,
       allTestsFinished,
       verbose,
       recordingPath,
       recordingOutputPath,
       adbDevicePool);
 }