Switch pkg packages, pub, and dartdoc to use package: imports.

utils/pub/source.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 source;
 
 import 'dart:async';
 
-import '../../pkg/pathos/lib/path.dart' as path;
+import 'package:pathos/path.dart' as path;
 
 import 'io.dart';
 import 'package.dart';
 import 'pubspec.dart';
 import 'system_cache.dart';
 import 'utils.dart';
 import 'version.dart';
 
 /// A source from which to install packages.
 ///
@@ skipping 198 matching lines @@
   Future<PackageId> resolveId(PackageId id) => new Future.immediate(id);
   
   /// Returns the [Package]s that have been installed in the system cache.
   Future<List<Package>> getCachedPackages() {
     if (shouldCache) throw "Source $name must implement this.";
   }
 
   /// Returns the source's name.
   String toString() => name;
 }