Get rid of DART_SDK in pub.

sdk/lib/_internal/pub/test/real_version_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 '../lib/src/sdk.dart' as sdk;
 
 import 'package:path/path.dart' as path;
 import 'package:scheduled_test/scheduled_process.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'test_pub.dart';
 
 main() {
   initConfig();
 
   // This test is a bit funny.
   //
   // Pub parses the "version" file that gets generated and shipped with the SDK.
-  // Most of the pub tests here generate a synthetic SDK directory so that we
-  // can tests against a known SDK state. But we want to make sure that the
-  // actual version file that gets created is also one pub can parse. If this
-  // test fails, it means the version file's format has changed in a way pub
-  // didn't expect.
+  // We want to make sure that the actual version file that gets created is
+  // also one pub can parse. If this test fails, it means the version file's
+  // format has changed in a way pub didn't expect.
   //
   // Note that this test expects to be invoked from a Dart executable that is
   // in the built SDK's "bin" directory. Note also that this invokes pub from
   // the built SDK directory, and not the live pub code directly in the repo.
   integration('parse the real SDK "version" file', () {
     // Get the path to the pub binary in the SDK.
     var pubPath = path.join(sdk.rootDirectory, 'bin',
         Platform.operatingSystem == "windows" ? "pub.bat" : "pub");
 
     var pub = new ScheduledProcess.start(pubPath, ['version']);
     expect(pub.nextLine(), completion(startsWith("Pub")));
     pub.shouldExit(0);
   });
 }