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

sdk/lib/_internal/pub/lib/src/command/cache.dart

Index: sdk/lib/_internal/pub/lib/src/command/cache.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/cache.dart b/sdk/lib/_internal/pub/lib/src/command/cache.dart
index f0559b763437a25d9c6d8e75dee0a5d7cdaf3808..432f09655357897b2a3afe7afe451737a2279a36 100644
--- a/sdk/lib/_internal/pub/lib/src/command/cache.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/cache.dart
@@ -11,13 +11,14 @@ 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());
+  }
 }