Introduce Sky packaged apps.

mojo/public/sky/rules.gni

+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Rules to generate packaged applications for Sky
+
+import("//build/module_args/mojo.gni")
+import("$mojo_sdk_root/mojo/public/dart/rules.gni")
+
+# Use this template to generate a .mojo Sky application. One of the source
+# files should be named main.sky; this file will be the entrypoint of the
+# application.
+template("sky_packaged_application") {
+  dart_packaged_application(target_name) {
+    sources = invoker.sources
+    if (defined(invoker.deps)) {
+      deps = invoker.deps
+    }
+    if (defined(invoker.uses_pub)) {
+      uses_pub = invoker.uses_pub
+    }
+    uses_sky = true
+  }
+}