Add support for configuration presets.

test/runner/configuration/platform_test.dart

 // Copyright (c) 2016, 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.
 
 @TestOn("vm")
 
 import 'dart:convert';
 
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_test.dart';
@@ skipping 162 matching lines @@
       """).create();
 
       var test = runTest(["."]);
       test.stdout.expect(containsInOrder([
         "+0: ./test_foo.dart: test_foo",
         "+1: All tests passed!"
       ]));
       test.shouldExit(0);
     });
 
-    test("doesn't OS-specific configuration on a non-matching OS", () {
+    test("doesn't apply OS-specific configuration on a non-matching OS", () {
       d.file("dart_test.yaml", JSON.encode({
         "on_os": {
           otherOS: {"filename": "test_*.dart"}
         }
       })).create();
 
       d.file("foo_test.dart", """
         import 'package:test/test.dart';
 
         void main() {
@@ skipping 63 matching lines @@
         var test = runTest([]);
         test.stderr.expect(containsInOrder([
           "Invalid timeout: expected unit.",
           "^^^^^"
         ]));
         test.shouldExit(exit_codes.data);
       });
     });
   });
 }