Move pub into sdk/lib/_internal.

utils/pub/source_registry.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_registry;
-
-import 'source.dart';
-
-/// A class that keeps track of [Source]s used for installing packages.
-class SourceRegistry {
-  final Map<String, Source> _map;
-  Source _default;
-
-  /// Creates a new registry with no packages registered.
-  SourceRegistry() : _map = <String, Source>{};
-
-  /// Returns the default source, which is used when no source is specified.
-  Source get defaultSource => _default;
-
-  /// Sets the default source. This takes a string, which must be the name of a
-  /// registered source.
-  void setDefault(String name) {
-    if (!_map.containsKey(name)) {
-      throw new StateError('Default source $name is not in the registry');
-    }
-
-    _default = _map[name];
-  }
-
-  /// Registers a new source. This source may not have the same name as a source
-  /// that's already been registered.
-  void register(Source source) {
-    if (_map.containsKey(source.name)) {
-      throw new StateError('Source registry already has a source named '
-          '${source.name}');
-    }
-
-    _map[source.name] = source;
-  }
-
-  /// Returns `true` if there is a source named [name].
-  bool contains(String name) => _map.containsKey(name);
-
-  /// Returns the source named [name]. Throws an error if no such source has
-  /// been registered. If [name] is null, returns the default source.
-  Source operator[](String name) {
-    if (name == null) {
-      if (defaultSource != null) return defaultSource;
-      throw new StateError('No default source has been registered');
-    }
-    if (_map.containsKey(name)) return _map[name];
-    throw new ArgumentError('No source named $name is registered');
-  }
-}