Update pub to new getter 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');
 
 #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;
+  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)) {
       // TODO(nweiz): Real error-handling system
       throw 'Default source $name is not in the registry';
     }
@@ skipping 26 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';
   }
 }