Add support for pub install.

utils/pub/command_install.dart

Index: utils/pub/command_install.dart
diff --git a/utils/pub/command_install.dart b/utils/pub/command_install.dart
new file mode 100644
index 0000000000000000000000000000000000000000..7161b26056a15c06ea737189bd8dc0e0e3940da0
--- /dev/null
+++ b/utils/pub/command_install.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2012, 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.
+
+/** Handles the `install` pub command. */
+class InstallCommand extends PubCommand {
+  String get description() => "install the current package's dependencies";
+
+  void onRun() {
+    packagesDir.installDependencies().then((_) {
+      print('Dependencies installed!');
+    });
+  }
+}