Reapply "Add a sleep function to dart:io"

utils/pub/command_cache.dart

 // Copyright (c) 2013, 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 command_cache;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:json' as json;
 
 import 'exit_codes.dart' as exit_codes;
 import 'log.dart' as log;
 import 'pub.dart';
 
 
 /// Handles the `cache` pub command.
-class CacheCommand extends PubCommand { 
+class CacheCommand extends PubCommand {
   String get description => "Inspect the system cache.";
   String get usage => 'pub cache list';
   bool get requiresEntrypoint => false;
-  
+
   Future onRun() {
     if (commandOptions.rest.length != 1) {
       log.error('The cache command expects one argument.');
       this.printUsage();
       exit(exit_codes.USAGE);
     }
-    
+
     if ((commandOptions.rest[0] != 'list')) {
       log.error('Unknown cache command "${commandOptions.rest[0]}".');
       this.printUsage();
       exit(exit_codes.USAGE);
     }
-    
+
     // TODO(keertip): Add flag to list packages from non default sources
     var packagesObj = <String, Map>{};
     for (var package in cache.sources.defaultSource.getCachedPackages()) {
       packagesObj[package.name] = {
         'version': package.version.toString(),
         'location': package.dir
       };
     }
 
     // TODO(keertip): Add support for non-JSON format
     // and check for --format flag
     log.message(json.stringify({'packages': packagesObj}));
-  }  
+  }
 }