Update pub to use new import syntax.

utils/pub/system_cache.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('system_cache');
+library system_cache;
 
-#import('io.dart');
-#import('package.dart');
-#import('source.dart');
-#import('source_registry.dart');
-#import('utils.dart');
-#import('version.dart');
+import 'io.dart';
+import 'package.dart';
+import 'source.dart';
+import 'source_registry.dart';
+import 'utils.dart';
+import 'version.dart';
 
 /**
  * The system-wide cache of installed packages.
  *
  * This cache contains all packages that are downloaded from the internet.
  * Packages that are available locally (e.g. from the SDK) don't use this cache.
  */
 class SystemCache {
   /**
    * The root directory where this package cache is located.
@@ skipping 41 matching lines @@
 
     var pending = _pendingInstalls[id];
     if (pending != null) return pending;
 
     var future = id.source.installToSystemCache(id);
     always(future, () => _pendingInstalls.remove(id));
     _pendingInstalls[id] = future;
     return future;
   }
 }