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

utils/pub/lock_file.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 lock_file;
 
 import 'dart:json' as json;
+
+import 'package:yaml/yaml.dart';
+
 import 'io.dart';
 import 'package.dart';
 import 'source_registry.dart';
 import 'utils.dart';
 import 'version.dart';
-import '../../pkg/yaml/lib/yaml.dart';
 
 /// A parsed and validated `pubspec.lock` file.
 class LockFile {
   /// The packages this lockfile pins.
   Map<String, PackageId> packages;
 
   LockFile._(this.packages);
 
   LockFile.empty()
     : packages = <String, PackageId>{};
@@ skipping 72 matching lines @@
     });
 
     // TODO(nweiz): Serialize using the YAML library once it supports
     // serialization. For now, we use JSON, since it's a subset of YAML anyway.
     return '''
         # Generated by pub. See: http://pub.dartlang.org/doc/glossary.html#lockfile
          ${json.stringify({'packages': packagesObj})}
         ''';
   }
 }