Update pub to use the new command runner API in args.

sdk/lib/_internal/pub/lib/src/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 pub.command.cache;
 
 import '../command.dart';
 import 'cache_add.dart';
 import 'cache_list.dart';
 import 'cache_repair.dart';
 
 /// Handles the `cache` pub command.
 class CacheCommand extends PubCommand {
+  String get name => "cache";
   String get description => "Work with the system cache.";
-  String get usage => "pub cache <subcommand>";
+  String get invocation => "pub cache <subcommand>";
   String get docUrl => "http://dartlang.org/tools/pub/cmd/pub-cache.html";
 
-  final subcommands = {
-    "add": new CacheAddCommand(),
-    "list": new CacheListCommand(),
-    "repair": new CacheRepairCommand()
-  };
+  CacheCommand() {
+    addSubcommand(new CacheAddCommand());
+    addSubcommand(new CacheListCommand());
+    addSubcommand(new CacheRepairCommand());
+  }
 }