Refactor Source to take the system cache as a parameter.

utils/pub/repo_source.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('dartlang_source');
 
 #import('dart:io');
 #import('dart:uri');
 #import('io.dart');
 #import('package.dart');
@@ skipping 33 matching lines @@
       return extractTarGz(httpGet(fullUrl), destDir);
     });
   }
 
   /**
    * The system cache directory for the repo source contains subdirectories for
    * each separate repository URL that's used on the system. Each of these
    * subdirectories then contains a subdirectory for each package installed from
    * that repository.
    */
-  String systemCacheDirectory(PackageId id, String parent) {
+  String systemCacheDirectory(PackageId id) {
     var parsed = _parseDescription(id.description);
     var url = parsed.last.replaceAll(new RegExp(@"^https?://"), "");
     var urlDir = replace(url, new RegExp(@'[<>:"\\/|?*%]'), (match) {
       return '%${match[0].charCodeAt(0)}';
     });
-    return join(parent, urlDir, "${parsed.first}-${id.version}");
+    return join(systemCacheRoot, urlDir, "${parsed.first}-${id.version}");
   }
 
   String packageName(description) => _parseDescription(description).first;
 
   bool descriptionsEqual(description1, description2) =>
     _parseDescription(description1) == _parseDescription(description2);
 
   /**
    * Ensures that [description] is a valid repo description.
    *
@@ skipping 29 matching lines @@
 
     var name = description["name"];
     if (name is! String) {
       throw new FormatException("The 'name' key must have a string value.");
     }
 
     var url = description.containsKey("url") ? description["url"] : defaultUrl;
     return new Pair<String, String>(name, url);
   }
 }