Add a "global activate" command to pub.

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

Index: sdk/lib/_internal/pub/lib/src/command/global.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/global.dart b/sdk/lib/_internal/pub/lib/src/command/global.dart
new file mode 100644
index 0000000000000000000000000000000000000000..cfd2996f2616dd43ce0cf45785ed2b6a89bf73ff
--- /dev/null
+++ b/sdk/lib/_internal/pub/lib/src/command/global.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2014, 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.global;
+
+import '../command.dart';
+import 'global_activate.dart';
+
+/// Handles the `global` pub command.
+class GlobalCommand extends PubCommand {
+  String get description => "Work with global packages.";
+  String get usage => "pub global <subcommand>";
+
+  final subcommands = {
+    "activate": new GlobalActivateCommand()
+  };
+}