Get rid of #source in pub.

utils/pub/package.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('package');
+
+#import('io.dart');
+#import('pubspec.dart');
+#import('source.dart');
+#import('source_registry.dart');
+#import('version.dart');
+
 /**
  * A named, versioned, unit of code and resource reuse.
  */
 class Package {
   /**
    * Loads the package whose root directory is [packageDir].
    */
   static Future<Package> load(String packageDir, SourceRegistry sources) {
     var pubspecPath = join(packageDir, 'pubspec');
 
@@ skipping 141 matching lines @@
   /**
    * The metadata used to identify the package being referenced. The
    * interpretation of this will vary based on the [source].
    */
   final description;
 
   PackageRef(this.name, this.source, this.version, this.description);
 
   String toString() => "$name $version from $source ($description)";
 }