Replace the existing unittest APIs with the new runner infrastructure.

test/loader_test.dart

Index: test/loader_test.dart
diff --git a/test/loader_test.dart b/test/loader_test.dart
index 95a4a8b14e19cde86747e94b6efad9d1b2d6b967..9ef3f6e33082c7c93d0b24ff9fafa4136f882e72 100644
--- a/test/loader_test.dart
+++ b/test/loader_test.dart
@@ -2,8 +2,6 @@
 // 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 unittest.loader;
-
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ -23,10 +21,9 @@ import 'dart:async';
 import 'package:unittest/unittest.dart';
 
 void main() {
-  var declarer = Zone.current[#unittest.declarer];
-  declarer.test("success", () {});
-  declarer.test("failure", () => throw new TestFailure('oh no'));
-  declarer.test("error", () => throw 'oh no');
+  test("success", () {});
+  test("failure", () => throw new TestFailure('oh no'));
+  test("error", () => throw 'oh no');
 }
 """;
 
@@ -83,7 +80,7 @@ void main() {
     test("throws a nice error if the package root doesn't exist", () {
       var loader = new Loader();
       expect(() => loader.loadFile(p.join(_sandbox, 'a_test.dart')),
-          throwsA(isFileSystemException(
+          throwsA(isLoadException(
               "Directory ${p.join(_sandbox, 'packages')} does not exist.")));
     });
   });