Reapply "Add a sleep function to dart:io"

utils/pub/command_cache.dart

Index: utils/pub/command_cache.dart
diff --git a/utils/pub/command_cache.dart b/utils/pub/command_cache.dart
index c3a3a3d53c16945436a64da7642d16af9ef6386c..eb77fd216a662264b568dc118b34f69ca5aa9420 100644
--- a/utils/pub/command_cache.dart
+++ b/utils/pub/command_cache.dart
@@ -14,24 +14,24 @@ 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()) {
@@ -44,6 +44,6 @@ class CacheCommand extends PubCommand {
     // TODO(keertip): Add support for non-JSON format
     // and check for --format flag
     log.message(json.stringify({'packages': packagesObj}));
-  }  
+  }
 }