Add a Pub test that runs against the real Dart SDK.

utils/tests/pub/install/sdk/check_out_test.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 pub_tests;
 
 import 'dart:io';
 
 import '../../test_pub.dart';
 import '../../../../../pkg/unittest/unittest.dart';
@@ skipping 14 matching lines @@
       pubspec({"name": "myapp", "dependencies": {"foo": {"sdk": "foo"}}})
     ]).scheduleCreate();
 
     schedulePub(args: ['install'],
         output: const RegExp(r"Dependencies installed!$"));
 
     packagesDir({"foo": "0.0.1234"}).scheduleValidate();
 
     run();
   });
+
+  // This is necessary to test that the "revision" file in the SDK remains in a
+  // format that Pub understands.
+  test('checks out a package from the real SDK', () {
+    ensureBuild();
+
+    dir(appPath, [
+      pubspec({
+        "name": "myapp",
+        "dependencies": {"unittest": {"sdk": "unittest"}}
+      })
+    ]).scheduleCreate();
+
+    schedulePub(args: ['install'],
+        output: const RegExp(r"Dependencies installed!$"),
+        realSdk: true);
+
+    dir(packagesPath, [
+      dir("unittest")
+    ]);
+
+    run();
+  });
 }