Move pub into sdk/lib/_internal.

sdk/lib/_internal/pub/test/install/hosted/cached_pubspec_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 'package:pathos/path.dart' as path;
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../../../pub/io.dart';
+import 'package:pub/src/io.dart';
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
 
   integration('does not request a pubspec for a cached package', () {
     servePackages([packageMap("foo", "1.2.3")]);
 
     d.appDir([dependencyMap("foo", "1.2.3")]).create();
@@ skipping 13 matching lines @@
     schedulePub(args: ['install'],
         output: new RegExp("Dependencies installed!\$"));
 
     // The update should not have requested the pubspec since it's installed
     // locally already.
     getRequestedPaths().then((paths) {
       expect(paths, isNot(contains("packages/foo/versions/1.2.3.yaml")));
     });
   });
 }