Add test that test.dart returns non-zero exit code for failing runs.

tests/standalone/io/test_runner_exit_code_script.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.
+
+// Simulates a use of test_progress during a failing run of test.dart.
+
+#import("../../../tools/testing/dart/test_progress.dart");
+#import("../../../tools/testing/dart/test_runner.dart");
+#import("../../../tools/testing/dart/test_options.dart");
+
+main() {
+  var progressType = new Options().arguments[0];
+  // Build a progress indicator.
+  var startTime = new Date.now();
+  var progress =
+    new ProgressIndicator.fromName(progressType, startTime, false);
+  // Build a dummy test case.
+  var configuration = new TestOptionsParser().parse(['--timeout', '2'])[0];
+  var testCase = new TestCase('failing_test.dart',
+                              [],
+                              configuration,
+                              (_) => null,
+                              new Set<String>.from(['PASS']));
+  // Simulate the test.dart use of the progress indicator.
+  progress.testAdded();
+  progress.allTestsKnown();
+  progress.start(testCase);
+  new TestOutput.fromCase(testCase, 1, false, false, [], [],
+                          new Date.now().difference(startTime));
+  progress.done(testCase);
+  progress.allDone();
+}