Update pub to use new import syntax.

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');
+library source_registry;
 
-#import('source.dart');
+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.
@@ skipping 43 matching lines @@
   Source operator[](String name) {
     if (name == null) {
       if (defaultSource != null) return defaultSource;
       // TODO(nweiz): Real error-handling system
       throw 'No default source has been registered';
     }
     if (_map.containsKey(name)) return _map[name];
     throw 'No source named $name is registered';
   }
 }